Computer Studies Notes Form 3

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1. Definition of Terms and Stages of Data Collection

Definition of terms and Stages of data collection

________________________________________

1. a) Data

Data is defined as a collection of raw facts (figures, letters, special symbols or a combination of both) that convey little meaning by themselves. example: in a statement like James, John and Caro

• what about them?

• why

• how

We actually don't know anything about these three people thus it does not have much meaning to us until its fully processed for us to understand

b) Information

Information is defined as data has undergone processing and is meaningful to the user when he/she needs it.

The statement simply indicates that information is not just a by-product of data processing, but it must have certain qualities for it to qualify to be a resource to the organization.

Thus the qualities of timeliness, correctness and relevancy must be observed for it to be good information. example:James, John and Caro were awarded certificates for being the cleanest students in our school.

this statement now satisfies our curiosity because it has been attached much more meaning useful to us but we need also to when.

This statement can therefore be regarded as information

c) Data Processing

Data processing can be regarded as the act of collecting data, manipulating it to get information through (input, Processing and output) and finally distributing it to the relevant organs for use.

Data Processing Cycle

Data Processing Platform

Data processing cycle are the stages (phases) through which data moves before it becomes information.

These stages include:

1. Data collection

2. Data input

3. Processing

4. Output

Stages of data processing cycle

i) Data Collection

Data collection is the act of collecting data from its point of origin to the computer in a form suitable for processing

Stages of Data Collection

Data collection is procedural, thus it attracts the following stages

A) Data Creation

Data creation is the process of capturing data from the source location using data capturing methods like:(scanning, digital camera, touch screen, voice input etc).

B) Data Transmission

This is a term used to refer to the transfer of data from the point of collection (source) to the point where processing is to be done (data processing department) this is possible through computer-to-computer communication, physically by post office or via courier services if the source is away from the data processing department.

C) Data Preparation

Data preparation is the term used to describe the process by which data is prepared and made ready for entry in the computer for processing.

ii) Data input

This is the process where the collected data is converted from human readable form into machine readable form (binary form)

To ensure quick and error free data the following features should be considered:

• Validation - this is the counter checking whether what is on the input document is exactly what is entered into the computer

• Media Conversion - this is the act of converting data from different storage medium e.g from a flash disk to a hard disk

• Sorting - Data should be arranged in a predefined order before being processed

iii) Processing

This is the manipulation of input data into a more meaningful output that can be regarded as being meaningful to the user.

Processing involves arithmetic, sorting and logical operations

iv) Output

This is the final activity in data processing cycle where the expected output (information) is displayed.

This information is then distributed to places (information dissemination) where its needed to influence decision making process.

Information dissemination may include: electronic presentations over radio or television, distribution of hard copies, broadcasting messages over the internet or mobile phones.

________________________________________

Questions 1. Define the following terms

a) Data Processing

b) Data processing cycle.

c) Data

d) Information

2. using an illustration, describe the four primary stages of the data processing cycle

3. Outline the stages of data collection

4. List the three feature involved during data input stage to minimize errors

5. What is the essence of output stage?

2. Description of errors in data processing

Description of errors in data processing

1. Introduction:

Computers make errors because people program them to make those errors.

Thus the acronym GIGO - Garbage in Garbage out- errors can be described as:

1) Transcription errors

2) Computation errors and

3) Algorithm errors

1) Transcription errors

Transcription errors occur during data entry. These errors include:

i) Misreading errors

ii) Transposition errors

i) Misreading errors

These errors are caused by incorrect reading of the source document by the user and hence entering wrong values e.g. a user may enter 5 instead of S or 0 instead of o and so forth.

ii) Transposition errors

These are errors that occur due to incorrect arrangement of characters. like putting characters in the wrong order. e.g. the user may enter 369 instead of 396.

However these errors can be avoided by using modern data capture devices like the bar code reader, optical character reader, digital cameras, scanners, configuring the right data-types in the database e.t.c.

2) Computation errors

These are errors that occur when an arithmetic operation does not produce the expected results

. They include:

overflow, underflow, truncation and rounding errors

a> Overflow

These are errors that occur from a calculation which appear too large to be stored in the allocated memory space. e.g. if a byte is represented by 8 bits, an overflow will occur if the result of a calculation gives a 9-bit number.

b> Underflow

Underflow (or "floating point underflow", or just "underflow") is a condition in a computer program where the result of a calculation is a smaller number than the computer can actually store in memory.

Arithmetic underflow can occur when the true result of a floating point operation is smaller in magnitude (that is, closer to zero) than the smallest value representable as a normal floating point number in the target datatype.

Underflow can in part be regarded as negative overflow of the exponent of the floating point value.

For example, if the exponent part can represent values from −127 to 127, then a result with absolute value less than 2−127 may cause underflow.

c> Truncation

Truncation errors result from having real numbers that have a long fractional part which cannot fit in the allocated memory space.

The computer would truncate or cut off the extra characters from the fractional part For example, a number like 0.784969 can be truncated to four digits to become 0.784.

The resulting number is not rounded off.

d> Rounding

Rounding errors results from raising or lowering a digit in a real number to the required rounded number.

For example, to round off 30.666 to one decimal place, we raise the first digit after the decimal point if its successor is more than 5.

In this case, the successor is 6 therefore 30.666 rounded up to one decimal place is 30.7. If the successor is below 5, e.g. 30.635, we round down the number to 30.6.

3) Algorithm errors

An algorithm is a set of procedural steps followed to solve a given problem. Algorithms are used as design tools when writing programs.

Wrongly designed programs would result in a program that runs but gives erroneous output.

Such errors that result from wrong algorithm design are referred to as algorithm or logical errors.

Data Integrity

Data integrity refers to the correctness and completeness of data entered in a computer or received from the information system.

Integrity is measured in accuracy, timeliness and relevancy of data

A> Accuracy

This is how close an approximation is to an actual value. example: in a number like 34.247545, 34.2475 is more accurate than than 34.2 this is because the deviation on the former is much lesser than the latter.

B> Timeliness

This is the relative accuracy of data in respect to the current state of affairs for which it is needed. Information should be available on time for decision making.

For example: In a data base to prepare worker's salaries, information on the presence of workers over the month should be processed on time before salary arrears are released every month.

C> Relevancy

Data entered into the computer must be relevant in order to get the expected output.

it must meet pertinent needs at hand and must meet the requirements of the processing cycle.

Way to minimize data integrity threats

1. Backup data on secondary storage devices or on online storage stores like Dropbox and Google Drive

2. Control access to data by enforcing security measures

3. Design user interfaces that minimize chances of invalid data entry

4. Using error detection and correction software when transmitting data

5. Using devices that directly capture data from the source such as bar code readers, digital cameras, optical character reader e.t.c.

Quiz

1. Define the following terms a) data processing b) data processing cycle

2. Using an illustration, describe the four primary stages of the data processing cycle

3. outline the stages of data collection

4. you may have come across the term garbage in garbage out (GIGO). what is its relevance to errors in data processing.

5. explain the two types of transcription errors

6. state three types of computational errors

7. a) define the term data integrity

b) give three factors that determine the integrity of data

C) state at least five ways of minimizing threats to data integrity.

3. Data Processing Methods

posted Jun 26, 2014, 7:08 AM by Maurice Nyamoti [ updated Feb 8, 2016, 4:52 PM ]

Data Processing Methods

Introduction:

There are three types of data processing methods namely:

1. Manual data processing

2. Mechanical data processing

3. Electronic Data Processing

Manual data processing

A paper and pen are used to process in manual data processing example:

Most schools in Kenya process their data manually especially while admitting form 1s.

As the students report, they are given a form to fill, these forms are filed by the school secretary and stored in the file cabinet- that is, if the school has 450 students, the school secretary will have those 450 files to handle thus retrieve, store, manipulate and update information which is a tedious job.

therefore manual data processing can also be defined as the physical entering and organization of data

Mechanical data processing

In mechanical data processing, data is processed with different mechanical devices.

This can include typewriters and calculators

Electronic Data Processing

Electronic Data Processing (EDP) can refer to the use of automated methods to process commercial data.

This means that, data processing, retrieval, storage, manipulation, sorting and part of analysis is done through automated methods using devices like computers.

Computer Files

A file can be defined as a collection of related records that give a complete set of information about a certain item or entity.

A computer file is a resource for storing information, which is available to a computer program and is usually based on some kind of durable storage.

Advantages of computerized/electronic filing system

1. Ease of access.

2. Speed of access.

3. Increased search facilities.

4. Capability to store huge amounts of information in a small space.

5. Portability - a pen drive or disc enables you to transport enormous amounts of data easily and discreetly.

6. Access to data can be monitored and/or restricted. thus enhancing data security

7. Its easier to update and modify information

8. Enhances data integrity and reduces duplication

Disadvantages of computerized/electronic filing system

1. Electrical/Electronic failure can cause temporary suspension of business or permanent loss of data.

2. Portability - copied information can be easily hidden on a disc or pen drive.

3. Data is not always secured by correct monitoring of access.

4. Information can be permanently deleted in error.

5. Hacking can release information that is data protected.

6. Cost of installing system.

Elements of a Computer File

A computer file is made up of three elements namely:

1. Characters

2. Fields

3. Records

Characters

A character refers to a letter, number or symbol that can be entered, stored and output by a computer.

This is the smallest element in a computer file.

Fields

A field is a single character or a collection of characters that represent a single entity Example:

Records

A record is a collection of related fields that represent a single entity.

Classification of Computer files

Computer files are classified as:

1. Logical files

2. Physical files

Logical Files

This is computer file viewed in terms of what data items it contains and details of what processing operations may be performed on the data items.

It does not have implementation specific information like field and data types, size and file types.

Physical Files

This is a computer file viewed in terms of how data is stored on a storage media and how the processing operations are made possible.

They have specific details such as characters per field and data type for each field.

Questions

1. State the three types of data processing methods

2. Define a computer file and state three advantages and three disadvantages of computer files

3. Define: (i) Character (ii) field (iii) record

4. Explain the two classifications of computer files

5. Distinguish between a manual file and a computer file

6. List at least three equipments used during mechanical data processing methods for processing

7. Why is a computer file described as 'durable'?

3. Types of Computer Processing Files

Types of Computer Processing Files

There are various types of files used for storing data needed for processing, reference or backup. However the main common files include:

Master files, Transaction, Reference, Backup, Report and sort file.

Master File

A master file refers to a collection of records pertaining to one of the main subjects of an information system, such as customers, employees, products and vendors.

Transaction (movement) file

This is a collection of transaction records.

The data in transaction files is used to update the master files, which contain the data about the subjects of the organization (customers, employees, vendors, etc.).

Reference File

This file is normally used for reference or look-up purposes. Look up information is that information which is stored in a separate file but is required during processing.

Backup File

A backup file is used to hold copies (backups) of data or information from the computers fixed storage (hard disk)

Report File

A report file is used to store relatively permanent records extracted from the master file or generated after processing.

Sort File

A sort file stores data which is arranged in a particular order

Questions

A. State uses of the following files:

1. Sort file

2. master file

3. reference file

4. report file

5. transaction file

6. backup file

B. Of the above files, which file can be used:

i. In a supermarket to fetch the price of a commodity from the master file

ii. In a supermarket to update the master file

iii. In a bank to extract and store some important records from the master file

iv. In a bank to arrange records of customers according to their bank deposits

v. By the government to a keep copy of listed employees in the master file who are about to retire in one year time

5. File Organization Methods

File Organization Methods

1. Introduction

File organization refers to the way data is stored in a file.

File organization is very important because it determines the method of access, efficiency, flexibility and storage devices to be used.

There are four methods of organizing files on a storage media namely:

Sequential, random, serial and indexed- sequential

Sequential

• A sequentially organized file consists of records arranged in the sequence in which they are written to the file (the first record written is the first record in the file, the second record written is the second record in the file, and so on).

As a result, records can be added only at the end of the file.

Attempting to add records at some place other than the end of the file will result in the file begin truncated at the end of the record just written.

• Sequential files are usually read sequentially, starting with the first record in the file.

Sequential files with a fixed-length record type that are stored on disk can also be accessed by relative record number (direct access).

• Records in sequential files can be read or written only sequentially.

• After you have placed a record into a sequential file, you cannot shorten, lengthen, or delete the record. However, you can update (REWRITE) a record if the length does not change. New records are added at the end of the file.

• If the order in which you keep records in a file is not important, sequential organization is a good choice whether there are many records or only a few. Sequential output is also useful for printing reports.

Advantages

1. Sorting makes it easier to access records

Disadvantages

1. Sorting does not remove the need to access other records as the search looks for a particular record

2. Sequential records cannot support modern technologies that require fast access to stored records

3. The requirement that all records be of the same size is sometimes difficult to enforce

Random

• In random file organisation, records are stored in random order within the file.

Though there is no sequencing to the placement of the records, there is however, a pre-defined relationship between the key of the record and its location within the file.

In other words, the value of the record key is mapped by an established function to the address within the file where it resides.

Therefore, any record within the file can be directly accessed through the mapping function in roughly the same amount of time.

The location of the record within the file therefore is not a factor in the access time of the record.

As such, random files are also known in some literature as direct access files.

• This method is normally used by optical disks like compact disks

Advantages

1. Quick retrieval of records

2. The records can be of different sizes

Serial

• Serial file organization is the simplest file organization method. In serial files, records are entered in the order of their creation.

As such, the file is unordered, and is at best in chronological order.

Serial files are primarily used as transaction files in which the transactions are recorded in the order that they occur.

• This type of access is normally used by magnetic tapes

Advantages

1. It is simple

Disadvantages

1. It is cumbersome to access because you have to access all preceding records before retrieving the one being searched

2. Wastage of space on medium in form of inter- record gap

3. It cannot support modern high speed requirements for quick records access Indexed- Sequential

• indexed file contains records ordered by a record key. Each record contains a field that contains the record key.

The record key uniquely identifies the record and determines the sequence in which it is accessed with respect to other records.

A record key for a record might be, for example, an employee number or an invoice number.

• An indexed file can also use alternate indexes, that is, record keys that let you access the file using a different logical arrangement of the records.

For example, you could access the file through employee department rather than through employee number.

1. a) this is listing raw data into a meaningful format called information

n6. Electronic Data Processing Modes

Electronic Data Processing Modes

Computers are programmed to process data in different ways.

Just like humans they can process shortest job first-SJF, First Come First Serve-FCFS or they can just Round Robin giving a time span, important/emergency jobs first-real time.

Computers can also multitask or multi-programming etc. Examples of processing modes are:

1. Online Processing

2. Real-Time processing

3. Distributed Processing

4. Time-Sharing

5. Batch Processing

6. Multitasking

7. Interactive Processing

Online Processing

• In this processing mode, data is processed immediately it is received.

• Example: When booking a seat on an airline, the seat is booked immediately.

This is to avoid problems of double-booking.

other example of online processing is when playing computer games online

Real-Time Processing

• In real time processing the computer processes the incoming data as soon as it occurs, up-dates the transaction file and gives an immediate response that would affect the events as they happen.

• There is no much difference with online processing however with real-time processing, the outcome of the processing is required immediately to influence decision making and not necessarily through online means but can be within a machine.

• Example: in nuclear power stations, a certain level of temperature is required to be maintained for effective disintegration of atoms.

If the temperatures are not controlled, the system may cause an emergency situation- like in increase or decrease in slight temperature fluctuations, therefore computers are used to control the air conditioning systems at the plant because they are programmed to provide instant answers upon a slight change in temperature has occurred- that is what we call real-time processing

• Another example: is the use of humidifiers and dehumidifiers in the computer lab, when there is a lot of humidity, computers turn on the dehumidifiers and vice versa

Distributed data processing

• These points to dividing (distributing) processing tasks to two or more computers that are located on physically separate sites but connected by data transmission media; there may be a central computer that receives input from the remote computers (terminals), processes the data and updates the master file.

If required, the output can be communicated back to the remote terminals.

• Example: When you withdraw money from a bank, your records are transacted and updated in the main server computer which will also update client computers across the bank branches divide.

Time-Sharing

• Just as the name suggests, time-sharing refers to many terminals connected to a central computer and given access to the central processing unit apparently at the same time this sounds like ‘round robin’.

Each user is allocated a time slice of the CPU in sequence.

• The amount of time allocated to each user is controlled by a multi-user operating system.

If a user’s task is not completed during the allocated time slice, he/she is allocated another time slice later in a round robin manner.

Batch Processing

• In batch processing, data is accumulated as a group (batch) over a specified period of time e.g. daily, weekly or monthly.

• The batch is processed at once. E.g. in a payroll processing system, employees details concerning number of hours worked, rate of pay, and other details are collected for a period of time, say one month.

These details are then used to process the payment for the duration worked.

other areas where batch processing can be applied include:

• Processing bank cheques

• Printing of bank statements

• Updating of a stock database

Multiprocessing

• Multiprocessing refers to the processing of more than one task apparently at the same time.

This is possible in computers like mainframes and network servers.

• A computer may contain more than one independent central processing unit which works together in a coordinated way.

At a given time, the processors may execute instructions from two or more programs or from different parts of one program simultaneously.

Multi-programming

• Also referred to as multitasking- refers to a type of processing where more than one program are processed apparently at the same time by a single central processing unit.

• Unlike multiprocessing, in multitasking, the computer has only one CPU. The computer allocates each program a time slice and decides what order they will be executed.

Interactive Processing

• There is a continuous dialogue between the user and the computer.

• As the program executes, it keeps on prompting the use to provide input or respond to prompts displayed on the screen

Advantages of electronic processing

1. Quick processing especially where all required data is available

2. Availability of data and information digitally

3. Distance between entities that are processing data is made non-significant

4. Support for information sharing and collaboration on a wider scale.

Disadvantages of electronic information processing

1. Security of data can be compromised during storage or while in transit on networks if appropriate measures are not taken

2. Lack of legal frameworks in many countries that should support electronic processing activities

3. Lack of ICT skills among many knowledge workers to support electronic data processing.

Topical Questions

1. What similarity is there between:

i> Online processing and real-time processing

ii> Multiprocessing and multi-programming

2. What differences are there between:

i. Online processing and real-time processing

ii. Multiprocessing and multi-programming

3. SHULE Secondary school Board of Governors has asked you to help them find a computer processing mode that they will introduce to enroll form one students each year that will allow them to confirm admissions, pay school fees without necessarily having to travel physically to the school.

Which processing mode would you recommend and why 4. Of the processing modes, which mode is effective for filling questionnaires online and why?

b) this are a set of stages that data passes through in order to be transformed into information

c) These are raw facts which do not have much meaning to the user

d) Processed data which has much meaning and can be used in decision making 2.

3. i) data collection

ii) input

iii) processing

iv) output

4. a) media conversion

b) input validation

c) sorting

5. Display of expected results (information) that can be used in decision making

Data representation in a computer

Data Representation refers to the methods used internally to represent information stored in a computer. Computers store lots of different types of information:

Text (this refers to letters, numbers and symbols)

Graphics (such as pictures, drawings and clipart)

Sound (voice data)

Instructions (computer commands)

At least, these all seem different to us. However, ALL types of information stored in a computer are stored internally in the same simple format: a sequence of 0's and 1's.

How can a sequence of 0's and 1's represent things as diverse as your photograph, your favorite song, a recent movie, and your term paper?

It sounds complicated. However you should understand that computers don’t understand our natural languages like Kiswahili, English or Kalenjin.

They have their own language called machine language. That means, what you type or speak into the computer is converted into a language that computers are able to understand.

In digital computers, the user input is first converted and transmitted as electrical pulses that can be represented by two distinct states ON and OFF or ‘1’ and ‘0’ respectively.

The sequence of ‘1’ and ‘0’ forms electrical signals that the computer can understand; the figure below shows the difference between a discrete signal (digital) and a continuous (analogue) signal

A digital signal refers to an electrical signal that is converted into a pattern of bits. Unlike an analogue signal, which is a continuous signal that contains time-varying quantities, a digital signal has a discrete value at each sampling point.

The precision of the signal is determined by how many samples are recorded per unit of time.

Parameters used with signals

AMPLITUDE (A) this is the maximum displacement that the waveform of an electrical signal can attain

FREQUENCY (f) this is the number of cycles made by the electrical signal in one second. Its measured in hertz (Hz) 1 cycle per second

Periodic time (T) periodic time is the reciprical of frequency i.e T=1/f When a digital signal is to be sent over analogue telephone lines e.g email, it has to be converted to analogue signal .

this is possible with the use of a device called the Modem derived from the words Modulation and Demodulation. Modulation stands for converting a digital signal to analogue and demodulation refers to converting an analogue signal to digital

Concepts of data representation in digital computers

Data and instructions cannot be entered and processed directly into computers using human language.

Any type of data, be it numbers, letters, special symbols, sounds or pictures must first be converted into machine readable form.

Due to this reason, it is important to understand how a computer together with its peripheral devices handle data in its electronic circuits.

On magnetic media and in optical devices.

Data epresentation in digital circuits

In digital circuits, when the circuit is ‘on’, its interpreted as a ‘1’ and when ‘off’ its interpreted as a ‘0’.

These ‘1s’ and ‘0s’ is what computers understand and its refered to as binary language.

Data representation in magnetic media

The presence of a magnetic field in one directionon magnet media is interpreted as ‘1’, while the field in the opposite direction is interpreted as ‘0’.

Magnetic technology is mostly used on storage devices which are coated with special magnetic materials such as iron oxide.

Data is written on the media by arranging the magnetic dipoles of some iron oxide particles to face in the same directionand some others in the opposite direction.

Data representation on optical media

In optical devices, the presence of light is interpreted as ‘1’ while its absence is integrated as ‘0’.

Optical devices use this technology to read or store data.

Take an example of a CD-ROM.

If the shiny surface is placed under a powerful microscope, the surface can be observed to have very tiny holes called pits.

The areas that do not have pits are called land.

Land reflects laser light that hits on the surface but bits don’t reflect.

The reflected pattern of light from the rotating disk falls on a receiving photoelectric detector that transforms the patterns into digital form.

Reasons for use of binary system in computers

Binary systems are:

Reliable

Occupy less space

Use less energy

Bits, bytes, nibble and word

Bits: a bit can be defined as a binary digit which can either be 0 or 1. It is the basic unit of data or information in digital computers.

Byte: a group of bits (often 8) used to represent a character is called a byte.

A byte is used to measure the memory of a computer

A nibble: half a byte, which is usually a grouping of 4 bits Word: two or more bytes make a word

Word length: measure of the number of bits in each word

Example: let 11110000 represent a binary figure

There are 8 bits in the figure. Count

These 8 figures make up a byte

1111 or 0000 is a nibble this is because they are 4 of the 8 figures thus half

11110000 and 11110000 are two figures thus a word

11110000 and 11110000 make a word that has 16 bits thus word length

Questions

1. Why is the binary number system used in data representation?

2. Explain the following terminologies as used with data representation:

(a) Word

(b) Nibble

(c) Byte

(d) Bit

(e) Word length

3. Define the following words

(a) Amplitude

(b) Frequency

(c) Periodic time

4. Explain the role of a modem in communication

(a) Using illustration, explain how data is represented:

(b) In electronic circuits

(c) On magnetic media

(d) On CD-ROM

1. Introduction- Elementary Programming Principles

Elementary Programming Principles

Introduction

programming is the art of designing computer programs. When designing these programs, there are a number of procedural steps that need to be observed and laid down.

Previously, systems used to operate by plugging and unplugging wires on the switch board which was more of a physical adventure than automated.

However, with programming devices, systems got automated due to software advancements and creations and that is how digital technology came into being courtesy of programming.

Computer Programming

Computers work by running a set of instructions called Programs (software or codes).

Programming involves creation of computer programs to solve a particular task.

When creating computer programs, one is likely to use programming languages which create a platform to create programs.

A programming language is a special set of symbols that can be translated into machine readable form by the computer when arranged in a particular sequence or order.

Each language has a special sequence or order of writing characters usually referred to as syntax.

Brief History of Programming Languages

Evolution of programming languages

- Years 50: Creation of high-level languages (closer to humans).

- Years 60: Expansion of specialized languages. Forth. Simula I. Lisp, Cobol. Trying unsuccessfully to impose general languages:Algol, PL / 1.

- Years 70: Duel between structured programming with Pascal and efficiency of C language. Basic generalized on personal computers from 1977, until the late 80s.

- Years 80: Experimentating other ways including objects. ML. Smalltalk.

On computers, we now use C, Pascal, Basic compiled.

- Years 90: Generalization of object-oriented programming with the performance of microcomputers.

Java, Perl, Python languages in addition to microphones.

- 2000s: Internet Programming (and future innovations, see end of text).

- Years 2010: Concurrency and asynchronicity. JavaScript and Go languages among others help to create online fluid applications.

First language

Ada Lovelace and Babbage and its nephew were writing programs for the project of "difference engine", and then the "analytical engine".

In 1945, the German K. Zuse, inventor of the Z3 computer would have defined an evolved language for this engine (with arrays and records).

Few documents of the epoch about this language exist.

Follow this web address to learn more about evolution of programming languages:

http://www.scriptol.com/programming/history.php

Description of terms used in Programming

Source Program

This is the program code that the programmer enters in the program editor window that is not yet translated into machine readable form.

The source program is usually created using a particular programming language like Pascal, C, C++, Visual Basic, Java e.t.c.

Object Code

This is program code that is in machine readable form.

A source code that is not in machine readable form must be translated into object code.

Translators

This refers to language processors such as assemblers, interpreters and compilers that convert the source program into object code.

Assemblers

An assembler translates assembly language into machine language that the computer can understand and execute.

Interpreter

An interpreter translates the source program line-by-line, allowing the CPU to execute one line before translating the next.

The translated line is not stored in the computer memory.

It means that every time, the program is needed for execution, it has to be translated.

This method of translating programs was very common in early computers that did not have enough memory to store the object code as a file that can be executed later.

Compiler

A compiler translates the entire source program into object code.

The object code file can be made into full executable program by carrying out another process known as linking which joins object code to all the other files that are needed for the execution of the program.

After the linking process, an executable file (application file) is generated.

This file is stored on a storage media such as a disk with a name that has a unique extension (.EXE).

Differences between interpreters and compilers

Interpreters Compilers

1. Translates the source program one statement at a time Translates the entire source code at once before execution

2. Translates the program each time it is run hence slower than compiling Compiled program (object code) can be saved on a storage media and run as required, hence executes faster than interpreted programs

3. Interpreted object code takes less memory compared to compiled program Compiled programs require more memory as the object file are larger.

2. Levels of Programming Languages- Low Level Languages

1. Levels of Programming languages

Programming languages are categorized into two levels namely:

1. Low- Level Languages

2. High-Level Languages

Low- Level Languages

A low-level programming language is a programming language that provides little or no abstraction from a computer's instruction set architecture.

Generally this refers to either machine code or assembly language.

The word "low" refers to the small or nonexistent amount of abstraction between the language and machine language; because of this, low-level languages are sometimes described as being "close to the hardware".

Low-level languages can be converted to machine code without using a compiler or interpreter, and the resulting code runs directly on the processor.

A program written in a low-level language can be made to run very quickly, and with a very small memory footprint; an equivalent program in a high-level language will be more heavyweight.

Low-level languages are simple, but are considered difficult to use, due to the numerous technical details which must be remembered.

There are two languages used in low level languages namely:

a) Machine language (First generation language)

b) Assembly Language (Second generation language)

Machine language (First generation language)

Sometimes referred to as machine code or object code, machine language is a collection of binary digits or bits that the computer reads and interprets.

Machine language is the only language a computer is capable of understanding.

  • Instructions are written using binary logic
  • They require many lines of logic to accomplish a task
  • This very code is hard for humans to understand unless he/she is equipped with special knowledge in machine level programming
  • Different CPUs have different machine codes this is in reference to the coding schemes we learned earlier like ASCII and EBCDIC
  • These programs are easy to execute by the CPU but hard to understand by humans

    Advantage Machine Language:

    The only advantage is that program of machine language run very fast because no translation program is required for the CPU.

    Disadvantages Machine Language:

    1. It is very difficult to program in machine language. The programmer has to know details of hardware to write program.

    2. The programmer has to remember a lot of codes to write a program which results in program errors.

    3. It is difficult to debug the program.

    Example:

    Machine Instruction Machine Operation

    00000000 Stop Program

    00000001 Turn bulb fully on

    00000010 Turn bulb fully off

    00000100 Dim bulb by 10%

    00001000 Brighten bulb by 10%

    00010000 If bulb is fully on, skip over next instruction

    00100000 If bulb is fully off, skip over next instruction

    01000000 Go to start of program (address 0)

    Assembly Language

    Sometimes referred to as assembly or ASL, assembly language is a low-level programming language used to interface with computer hardware.

  • They were developed to overcome the difficulties of understanding and using machine languages
  • It attempted to make computer languages readable
  • This language allowed programmers to write programs as a set of symbolic operation codes called Mnemonics- this is a shortened two or three letter words.
  • Programs written in assembly language require an assembler in order convert them into machine language that the computer can understand.
  • Assembly language is machine dependent- this means, a program written for one computer cannot be used on another.

    The following disadvantages are observed with the assembly languages.

    1. It is time consuming for an assembler to write and then test the program.

    2. Assembly language programs are not portable.

    3. It is necessary to remember the registers of CPU and mnemonic instructions by the programmer.

    4. Several mnemonic instructions are needed to write in assembly language than a single line in high-level language. Thus, assembly language programs are longer than the high language programs.

    Example:

    MOV r0, #0C ;load base address of string into r0

    LOAD: MOV r1,(r0) ;load contents into r1

    CALL PRINT ; call a print routine to print the character in r1

    INC r0 ;point to next character

    JMP LOAD ;load next character

    ________________________________________

    1. High level languages

    • These languages are close to human languages such that humans can read and understand easily than low level languages

    • These languages are machine independent this means that they are not subject to hardware models and configurations

    • These languages are classified into five groups namely:

    I. Third generation languages (3GLs)

    II. Fourth Generation Languages (4GLS)

    III. Fifth generation Languages (5GLs)

    IV. Object Oriented Languages (OOPs)

    V. Web scripting Languages

    Third generation languages (3GLs)

    • These languages are also called procedural or structured languages; this means that these are languages that make it possible to break a program into components called modules each performing a particular task.

    This is referred to as structured programming

    • In structured programming

    i. Large programs can be broken down into smaller sub programs each performing a single task

    ii. Use of a few simple control structures in problem solving. These control structures include sequence, selection and iteration

    • Structured programming languages are flexible, easier to read and modify

    Examples:

    Pascal: was initially developed for teaching structured languages

    Fortran: (FORmulaTRANslator) this language was developed for mathematicians, scientists and engineers. It involves writing programs with mathematical expressions.

    COBOL: (common business oriented language); this language was developed to solve business problems e.g. developing data processing applications such as computer – based inventory control systems.

    Basic: (Beginners All- Purpose Symbolic Instructional Code); this language was developed to initially enable students learn programming.

    This is a simple general purpose language used for developing business and educational applications.

    This was the first high level language that was available for microcomputer users.

    C: This is a programming language mainly used for developing system software such as the operating system.

    It is one of the most popular and powerful high – level languages in the business world because of its ability to provide the programmer with powerful features of low level languages and at the same time easily understandable as a high level language.

    ADA: this is a language named after the first lady programmer.

    Ada Lovelace. Ada is suitable for developing military, industrial and real-time systems

    Fourth Generation Languages (4GLs)

    Fourth generation languages make programming an even easier task than the third generation language because they present the programmer with more programming tools which include:

    Command buttons, forms, textboxes, Combo boxes etc.

    Here, selects graphical objects on the screen called controls then uses them to create designs on a base form.

    The programmer may also use an application generator works behind the scenes to generate the necessary code, hence the programmer is freed from tedious work of writing the code.

    Examples of fourth generation languages

    Visual Basic, Delphi Pascal and Visual COBOL

    Fifth Generation Languages (5 GLs)

    These languages are designed to depict human-like intelligence.

    With these languages, the programmer only worries about what problem needs to be solved and what conditions need to be met without worrying about how to implement an algorithm to solve them.

    Examples:

    PROLOG, Mercury, Lisp and OCCAM

    Object-Oriented Programming Languages (OOPs)

    The concept behind OOPs is to look at a program as having various objects interacting to make up a whole.

    Each object has specific data values that are unique to it (called state) and a set of the things it can accomplish called (functions or behavior).

    This process of having data and functions that operate on the data within an object is called encapsulation.

    Several objects can then be linked to form a complete program.

    Examples:

    C++, Java and SmallTalk

    Web Scripting Languages

    The World Wide Web has thrown up a number of new scripting languages specifically designed for web page design.

    It has also seen an upsurge in popularity of some older languages originally designed for other purposes but which happen to be well-suited for web applications.

    The following identifies some of the major scripting languages associated with Web page design:

    Examples:

    • HTML (HyperText Markup Language). All web pages are written using HTML (although some of the scripting languages listed below may also be used to provide more versatility).

    HTML is not really a programing language.

    It is essentially a set of tags which can be embedded within Ascii text to control how the text should be displayed when viewed in a web browser.

    • DHTML (Dynmaic HTML). DHTML is not a language at all. Rather it is a name applied to various technologies (e.g. Cascading Style Sheets (CSS), Document Object Model (DOM) and scripting languages such as JavaScript) used to supplement HTML to provide web pages with dynamic content.

    DHTML does not depend upon plug-ins and should in theory run on any HTML 4 compatible browser. Processing is client-side.

    • JavaScript. Although it shares some similarities with Java, JavaScript is not a subset of Java. Java and JavaScript were developed independently.

    JavaScript (originally called LiveScript) is a scripting language developed by Netscape for enhancing web pages.

    It was probably renamed JavaScript to cash in on the popularity of Java.

    This has unfortunately resulted in a lot of confusion as Java may also be used to enhance webpages. JavaScript is primarily used for client-side processing.

    • JScript is a Microsoft version of JavaScript. JScript is generally used for client-side processing, but it may also be used for server-side processing.

    Active Server Pages, for example, may be set-up to run JScript rather than VBScript.

    • VBScript is a subset of Visual Basic for Applications (VBA). VBScript is an interpreter language, whereas VB can be compiled.

    VBScript is often used for server-side scripting and is the default language for Active Server Pages (ASP).

    It may also be used fot client-side scripting (although it is currently only supported by Internet Explorer).

    • Perl (Practical Extraction and Report Language) is a powerful text processing language developed by Larry Wall.

    It originated on Unix platforms, but interpreters are now available for Windows and Macintosh.

    Scripts can be easily ported between platforms.

    Although CGI scripts can be written in other languages (e.g. C or Visual Basic), Perl is often the language of choice for CGI (Common Gateway Interface) scripts.

    Although useful for web applications, Perl is an extremely versatile language and may also be used for a multitude of non-web related purposes.

    • PerlScript is a subset of Perl. It may be used for ActiveX and Active Server Pages.

    • Tcl (Tool Command Language) - sometimes pronounced tickle - was developed by John Ousterhout.

    Like Perl it may be used for CGI scripting or for writing applications.

    It may be also used to write client-side scripts which run on the user's browser.

    • PHP was created in 1994 by RasmusLerdorf to add dynamic content to an HTML page.

    PHP initially stood for 'Personal Home Page', but now it is generally translated as 'PHP Hypertext Preprocessor'.

    The PHP code is embedded within the HTML code between special tags. When the page is accessed the server processes the PHP code and then sends the output from the script as HTML code to the client.

    • CFML (ColdFusion Markup Language) is a tag-based scripting language developed by Allaire (now merged with Macromedia) as part of the ColdFusion system for dynamic web page creation and database access.

    The CFML commands are embedded in HTML files. The results of database queries are converted into HTML by the server.

    • Ajax is an abbreviation for Asynchronous JavaScript and XML.

    It is not a language as such, but a group of interrelated client-side web development techniques used to create interactive web applications.

    Advantages and disadvantages of low-level and high level languages

    Advantages of low level languages

    • The CPU understands machine language directly without translation

    • The processor executes them faster because complex instructions already broken down into smaller simpler ones

    • Low level languages are stable and hardly crash or break down once written

    Disadvantages of low level languages

    • They are difficult and cumbersome to use and learn

    • They require highly trained experts both to develop and maintain programs

    • Removing errors (debugging) In a low level language programs is difficult

    • Low level programs are machine dependent i.e. they are not transferable from one hardware or software platform to another.

    Thus, they are not portable

    Advantages of high level languages

    • High level languages are portable i.e. they are transferable from one computer to another

    • They are user friendly and easy to use and learn

    • Are more flexible. Thus, enhancing creativity and increasing productivity

    • Are easier to debug (correct errors)

    Disadvantages of high level languages

    • Due to large volume of code involved when generating, these programs are slower in processing

    • They have to be interpreted or compiled to machine readable form before the computer can execute them.

    • They require large computer memory to run it

    Topical questions

    1. Define the term computer program

    2. What is programming?

    3. State three advantages of high level languages over low level languages

    4. List four examples of high level languages and for each, state its most appropriate application area

    5. Why is an executable file unique when compared to any other file?

    6. Differentiate between a compiler and an interpreter. Why did early computers work well with interpreters?

    7. List the various examples of programming languages per generation

    8. Write the following in full:

    A) HTML

    B) OOP

    9. Distinguish between source program and object code in programming

    10. State one advantage of machinery language over the other languages

    11. Define the term encapsulation as used in object oriented programming languages

    12. Distinguish between:

    a) Low level and high level languages

    b) Assembly and machine languages

    c) Third generation and forth generation languages

    d) Object Oriented Languages and Web Scripting Languages

    13. Explore necessary advantages and disadvantages of low level and high level languages stating two examples of each.

    Program Development 1. Program Development

    Introduction

    Development of programs is the art of preparing and designing necessary structures to come up with computer instructions that can be used to accomplish a task in the computer.

    There are six procedural steps involved in program development namely:

    1> Problem recognition

    2> Problem definition

    3> Program design

    4> Program coding

    5> Program testing and debugging

    6> Implementation and maintenance

    There should be some kind of uniformity and relevance in execution from one stage to another and in every stage, documentation is necessary.

    The diagram below elaborates this.

    Problem Recognition

    • This is the understanding and interpretation of a particular problem.

    To understand these problems, you need to highlight key words like: what needs to be computed, saved, compared, sorted, input etc.

    • To understand these problems, the programmer should:

    A> Talk to users in order to assess their situations

    B> Understand problems that need solutions

    C> Siege an opportunity to develop the new system

    D> Study the new directive given by the management requiring a change in the status quo

    E> Make a formal presentation of the system being designed

    Problem Definition

    • This is also referred to as problem analysis.

    • Here the programmer tries to determine or define the likely input, processing activities and the expected output using the keyword outlined at the problem recognition stage.

    • Finally, the boundaries of the expected program will have been established. In case several methods are identified that can be used to solve the same problem, then the best alternative should be chosen.

    Program design

    • This is the actual processing of the program or problem solving logic called the algorithm.

    • An algorithm refers to a definite number of logical steps that a program follows in order to solve a problem.

    It is the programmer who will usually come up with the algorithm after carefully analyzing the requirements specifications.

    • Most programs are not holistic, rather monolithic which means they are made up of several units called modules which work together to form the whole.

    • In modular programming, each module performs a specific task.

    This approach makes a program flexible, easier to read and carry out error correction.

    • This stage enables the programmer to come up with models of the expected program.

    The models show the flow of events and data throughout the entire program from the time data is input to the time the program gives out expected information.

    Program Coding

    • This is the art of converting a program design into an equivalent program.

    • This is possible by coding the program with the use of a specific programming language like: Java, Pascal, C++, Visual basic etc.

    • To code these programs, one needs a translator which converts source program into object code like assemblers, interpreters and compilers

    Program testing and debugging

    • This stage involves removing errors from the program (debugging) and execution to test its integrity.

    • There are two possible errors to debug:

    1> Syntax error

    These are errors that originate from improper use of language syntax (grammar, spelling, spacing, punctuation and skipping syntax) syntax- is the set of rules that defines the combinations of symbols that are considered to be a correctly structured document or fragment in that language.

    For example: in most programming languages, declaration lines end with a semi-colon, failure to insert a semi-colon can result into a syntax error

    Consider this PHP code:

    echo "My first PHP script!";

    If words like “echo” is misspelled like “icho” or “?” is missing at the start line or end line or quotations are missing in the statement “My first PHP script!" can lead to syntax error

    2> Logical errors

  • They are not detectable by the translator.

    The program runs but gives wrong output or halts during execution

    Example: consider the PHP code above

    The user may mistakenly alter the statement i.e. instead of typing echo "My first PHP script!" he/she types echo "My second PHP script!"

    The code will execute but the output will be wrong.

    Therefore, logical errors are done due to entry of logical parameters

    Methods of error detection

    - There are several methods of testing the program for errors.

    These include:

    1> Desk checking (dry-run)

    This involves going through the program while still on paper before entering it in the program editor.

    This helps the programmer to detect the most obvious syntax and logical errors

    2> Using debugging utilities

    This involves entering the program in the program editor and trying to run debugging utilities to correct syntax errors

    3> Using test data

    The programmer enters various data variations and extremes including data with errors to test whether the system will grind to halt

    Implementation and maintenance

    Implementation

    - This is the actual delivery and installation of the new program to be ready for use.

    Review and maintenance

    Proper training and post implementation support of users will always reduce the chances of having those entering invalid data that can crash the program.

    Program documentation

    • This is writing of formal support materials explaining how the program was developed

    • Documentation can be used by users, installed by operators and modified by programmers

    • All stages of the program development should be documented in order to help during future modification of the program.

    • Documentation is either internal or external

    • Internal documentation: is written as program comments that cannot be executed by the program editor. They help programmers to understand the source code

    • External documentation: refers to reference materials such as user manuals printed as booklets. User manuals are common examples of external documentation.

    • There are three target groups of external documentation namely:

    1. User oriented documentation: these type enables the user to learn how to use the program as quickly as possible and with little help from the program developer

    2. Operator oriented documentation: it is meant for computer operators such as the technical staff. It helps them to install and maintain the program

    3. Programmer oriented documentation: it is a detailed documentation written for skilled programmers.

    This documentation provides necessary technical information to help in future modification of the program.

    In this type of documentation, all stages of the program development should be documented because:

    • There may come a need to revise or modify the program

    • Other programmers may think of ways of improving your program.

    Summary (modern):

    Six Steps of PDLC

    Step Procedure Description

    1 Analyze the problem

    Precisely define the problem to be solved, and write program specifications – descriptions of the program’s inputs, processing, outputs, and user interface.

    2 Design the program

    Develop a detailed logic plan using a tool such as pseudo code, flowcharts, object structure diagrams, or event diagrams to group the program’s activities into modules; devise a method of solution or algorithm for each module; and test the solution algorithms.

    3 Code the program

    Translate the design into an application using a programming language or application development tool by creating the user interface and writing code; include internal documentation – comments and remarks within the code that explain the purpose of code statements.

    4 Test and debug the program

    Test the program, finding and correcting errors (debugging) until it is error free and contains enough safeguards to ensure the desired results.

    5 Formalize the solution

    Review and, if necessary, revise internal documentation; formalize and complete end-user (external) documentation

    6 Maintain the program

    Provide education and support to end users; correct any unanticipated errors that emerge and identify user-requested modifications (enhancements).

    Once errors or enhancements are identified, the program development life cycle begins again at Step 1.

    Trial Questions

    1. Give one advantage of compiling a program rather than interpreting it

    2. Outline at least six stages of program development in their respective order

    3. Highlight two disadvantages of monolithic programs

    4. State two advantages of modular programming

    5. In what stage of the development does program documentation justify your answer

    6. Differentiate between a flowchart and pseudo code

    7. What is a program bug?

    8. Explain why it is important to test a program before implementing it.

    5. Development of Algorithm- pseudocodes

    Development of Algorithm

    1. Development of algorithms

    Development of algorithms can be defined as logical steps that a program follows in order to solve a problem.

    Various tools are used to depict algorithms.

    They include:

    - Decision trees

    - Decision tables

    - Flowcharts and

    - Pseudo codes

    Pseudo codes A pseudo code is a set of statements written in a human readable language but expressing the processing logic of a program.

    - Pseudo codes are not executable by the computer

    Guidelines for designing a good pseudo code

    To design a good pseudocode, proceed as follows

    1. The statement must be short, clear and readable

    2. The statements must not have more than one meaning i.e. should be unambiguous

    3. The pseudo code lines should be clearly outlined and indented clearly

    4. A pseudo code should show clearly the start and stop of executable statements and the control structures (to be discussed later in the section)

    5. The input, output and processing statements should be clearly stated, using keywords such as

    Several keywords are often used to indicate common input, output, and processing operations.

    Input: READ, OBTAIN, GET

    Output: PRINT, DISPLAY, SHOW

    Compute: COMPUTE, CALCULATE, DETERMINE

    Initialize: SET, INIT

    Add one: INCREMENT, BUMP

    Example:

    Write a pseudo code that can be used to prompt the user to enter the diameter of a circle which will be used to calculate the perimeter and area of the circle

    Answers

    Start

    PRINT “enter diameter parameter”

    READ D

    PERIMETER = 22/7*D

    AREA = 22/7*D/2*D/2

    PRINT PERIMETER

    PRINT AREA

    Stop

    Trial Questions

    1. Write a pseudo code that can be used to prompt the user to enter two numbers, calculate the sum and average of the two numbers and then display the output on the screen

    2. Write a structured algorithm that would prompt the user to enter the length and width of a rectangle, calculate the area and perimeter then display the result

    3. Write a pseudo code for a program that can be used to classify people according to the age limit. If a person is more than 20 years; output “adult” else output “young person” 4. What factors do you consider when designing a good pseudo code

    5. What is the importance of writing algorithms

    5.1-FlowChart

    Flow Charts

    Flow charts are used to represent any well defined sequence of activities. they are used to convey in diagrammatic form, the logic, processing operations and flow of control required of a computer program

    1. Uses Of Flowcharts

    Flowcharts are used by programmers to:

    1. To plan the structure of a program before it is written

    2. To describe the structure of a program after it has been written

    Flowchart Symbols

    Flowchart symbols are combined with short text clues which are a form of shorthand understood by programmers. Below is a list of symbols:

    Symbol Meaning

    Guidelines for Drawing a Flowchart

    1. there should be only one entry/starting point and one exit point of the program algorithm - except for decisions and connectors

    2. Use the correct symbol at each stage in the flowchart

    3. The logical flow should be clearly shown using arrows.

    4. Use connectors to reduce the number of flow-lines

    5. Add notes if necessary, but don't clutter the diagram

    6. Lines should ideally be vertical or horizontal

    6. Program Control Structures

    Program Control Structures Introduction:

    program control structures are blocks of statements that determine how statements are to be executed, in structured programming languages, there are three control structures namely; sequence, selection and iteration (looping)

    Subpage Listing

    • 1. Sequence

    • 2. Selection

  • Selection Examples

  • Selection Questions

    • Iteration (Looping)

  • The FOR Loop Examples

  • The FOR Loop Questions

    Review Questions

    1. Sequence

    posted Jan 6, 2015, 11:59 AM by Maurice Nyamoti [ updated Jan 6, 2015, 12:19 PM ]

    Sequence

    In this structure, the computer reads instructions from a program file starting from the first top line and proceeding downwards one -by -one to the end.

    This is called sequential programming execution i.e.

    In sequential program execution, the computer perform tasks that are arranged sequentially one after another.

    Just like in a school system, a std5 student must first pass ECD, std 1 - 4 before std 5 in that sequence.

    2. Selection

    posted Jan 6, 2015, 12:36 PM by Maurice Nyamoti [ updated May 6, 2015, 11:07 AM ]

    Selection

    In selection control, execution of statements depends on a condition which is either a true or false

    There are four types of selection controls. Namely:

    1. IF.....THEN

    2. IF.....THEN.....ELSE

    3. NESTED IF

    4. CASE SECTION

    IF....THEN

    The IF....THEN selection is used if only one option is available. All other options are ignored

    Format:

    IF THEN

    Statements;

    ENDIF

    Flowchart Sample

    IF....THEN....ELSE

    This type of selection is suitable where there are two available options

    General Format

    IF THEN

    Statements;

    ELSE

    Statements;

    EndIF

    Flowchart Sample

    Nested IF Selection

    This type of selection is used where two or more options have to be considered to make a selection.

    General Format

    IF THEN

    statements

    ELSE

    IF THEN

    statements

    ELSE

    IF THEN

    Statements

    ELSE

    Statements

    ENDIF

    ENDIF

    ENDIF

    Flowchart Sample

    CASE Construct

    This is an alternative to the Nested IF especially where there are several options to choose from.

    Its preferred because it reduces the many lines of code.

    However, the boolean expression for the case selection can only be expressed using integers and alphabetic characters only.

    The General format should be

    CASE integer OF or

    CASE Char OF

    Example:

    Case x of

    label 1: statement 1

    label 2: statement 2

    label 3: statement 3

    label n: statement n-1

    lse

    statement

    Endcase

    Iteration (Looping)

    Iteration (Looping)

    1. Introduction

    Iteration is also referred to as looping or repetition. Its designed to execute the same block of code again and again until a certain condition is fulfilled.

    The three main looping controls are:-

    1. The WHILE Loop

    2. The REPEAT....UNTIL Loop

    3. The FOR Loop

    The WHILE Loop

    The "WHILE" loop is used if a condition has to be met before the statements within the loop are executed.

    General Format

    WHILE condition DO

    statement

    ENDWHILE

    The REPEAT....UNTIL loop

    The REPEAT....UNTIL loop allows the statements within it to be executed at least once since the condition is tested at the end of the loop.

    General Format

    REPEAT

    statements

    UNTIL

    The FOR Loop

    The FOR loop is used in circumstances where the execution of the chosen statements has to be repeated a predetermined number of times.

    General Format

    //pseudocode for 'FOR" loop that counts from the lower limit

    FOR loop variable = lower limit to upper limit DO

    statements

    ENDFOR

    //pseudocode for a 'FOR' loop that counts from the upper limit down to lower limit

    FOR loop variable = upper limit DOWN TO lower limit DO statements;

    ENDFOR

    System Development

    1. What is a system?

    posted May 2, 2015, 8:35 AM by Maurice Nyamoti [ updated May 2, 2015, 8:38 AM ]

    What is a system?

    A system is a set of organized components which interact in a given environment and within a specified boundary to achieve collective goals and objectives that are emergent Example of a system is a computer system. i.e.

    2. Description of a System

    posted May 2, 2015, 8:56 AM by Maurice Nyamoti [ updated May 2, 2015, 8:56 AM ]

    A system can either be described as either:

    1. Soft System or

    2. Hard System

    Soft System

    A system is described as soft because of the following characteristics:

    1. Boundaries keep on changing

    2. Goals and Objectives usually conflict due to human factors like attitudes and preferences

    3. Exact measures of performance cannot be clearly captured Hard Systems

    A system is said to be hard because of the following characteristics:

    1. Goals and objectives can clearly be defined

    2. Outcomes of the systems processes are predictable and can be modeled accurately 3. Characteristics of Systems

    posted May 2, 2015, 9:44 AM by Maurice Nyamoti [ updated May 2, 2015, 9:55 AM ]

    All systems have some similar characteristics as illustrated below:

    1. Holistic thinking

    A system is considered as a whole because many entities will work together to make a complex whole

    example:

    a human body is a complex whole made up of small entities like cells, chromosomes, enzymes, water, bones etc.

    2. Subsystems

    A system is made up of different components (subsystems)

    example:

    a human body system is made up of other sub-systems like; circulatory system, digestive system, neural systems etc.

    3. Boundary and Environment

    Each system has a space (boundary) within which the components operate.

    A system has two types of entities namely: internal and external entities.

    An internal entity operates from within the system boundary like the liver of a human body however, external entities operate from outside the boundary but are part of the system i.e. Food and Air in a human body

    4. Purpose

    The purpose of each system is to perform a particular task or achieve a goal.

    Example:

    The purpose of a human body system is to support life

    5. Process

    A system has the obligation to transform or process data from one state to another Example:

    In a human digestive system, food as transformed into nutrients like proteins and vitamins while the remaining is discharged as waste

    6. System Entropy

    The word entropy means decay. Systems decay over time.

    example:

    A human body eventually dies after a period of time when subsystems cannot support it anymore

    7. Inputs and Outputs

    A system communicates with environment by receiving inputs and giving outputs

    example:

    In a human body system, it takes food as an input and gives output through excretory process

    8: Open VS Closed Systems

    A system can be described as either open or closed. An open system receives input and gives output while a closed system does not.

    9. Control

    A system adapts to changes in the environment in order to give the expected output or to perform to the expected level.

    This is possible through the feedback which can be used to influence inputs

    example:

    If a human body is ill, the brain system sends a feedback (pain) this feedback will influence the person to seek medical care.

    4. Information System

    • An Information System is a man-made system that facilitates an organization’s operational functions and supports management decision making by providing information that managers can use to plan and control the activities of the firm.

    • is the collection of technical and human resources that provide the storage, computing, distribution, and communication for the information required by all or some part of an enterprise.

    • Management Information System (MIS) is a planned system of collecting, storing, and disseminating data in the form of information needed to carry out the functions of management.

    Purpose of information Systems

    1. Supporting information processing ~ by enhancing tasks such as data collection, processing and communication

    2. Helping in decision making ~ by collecting operational data, analyzing it and generating reports that can be used to support the decision making processing

    3. Enable sharing of information

    Why develop new information systems?

    1. New opportunities ~ a chance to improve quality of internal processes and services delivery in the organisation

    2. Problems ~ Need to solve problems at hand

    3. Directives ~ Change in policy or rules buy the company or Government

    Role of a System analyst

    A systems analyst is an IT professional who specializes in analyzing, designing and implementing information systems.

    System analysts assess the suitability of information systems in terms of their intended outcomes and liaise with end users, software vendors and programmers in order to achieve these outcomes.

    1. Examine existing IT systems and business models;

    2. Analyses systems requirements;

    3. Implement, configure and test feasible solutions.

    4. Liaise and report to internal and external clients and stakeholders, including colleagues and developers.

    5. Is involved throughout the development process. The analyst acts as liaison between the client and the developers.

    6. Conduct a cost analysis and agree the time frame to implement the proposed solution. They specify and shape the system requirements and operations, the user interface and output and present the proposal to the client.

    7. Is the overall project manager of the information system being implemented

    5. Theories of Development

    Subpage Listing

    • 1. Introduction on theories of system development

    • 2. Stages of system Development

    1. Introduction on theories of system development

    The aim of all these theories and methods is to identify business requirements and to develop information systems that effectively meet them

    Some of these theories include:

    1. Traditional approach

    2. Rapid Application Development (RAD)

    3. The structured approach

    1. Traditional Approach

    It relies mostly on the skills and experience of individual staff members carrying out the project. There are no formal procedures followed and therefore the success of the system is dependent on individual effort.

    In this approach, the manual system is replaced with a computerised one without change in overall structure of the former system, hence the weaknesses of the former system are not addressed and are carried forward to the new system.

    2. Rapid Application Development (RAD)

    RAD is also known as prototyping. A prototype is a sample used to test a concept or a process this is a concept that products can be developed faster and of higher quality through:

    • Gathering requirements using workshops or focus groups

    • Prototyping and early, reiterative user testing of design

    • The re-use of software components

    • A rigidly paced schedule that defers design improvements to the next product version

    • Less formality in reviews and other team communication

    Advantages of the RAD model:

    1. Reduced development time.

    2. Increases re-usability of components

    3. Quick initial reviews occur

    4. Encourages customer feedback

    5. Integration from very beginning solves a lot of integration issues.

    Disadvantages of RAD model:

    1. Depends on strong team and individual performances for identifying business requirements.

    2. Only system that can be modularized can be built using RAD

    3. Requires highly skilled developers/designers.

    4. High dependency on modeling skills

    5. Inapplicable to cheaper projects as cost of modeling and automated code generation is very high.

    3. The Structured Approach

    Structured approach involves a set of stages that should be followed when developing a system. Each stage is documented in specifying the activities that should be carried out.

    2. Stages of system Development

    There are seven stages in system development lifecycle namely:

    Problem recognition and definition

    In this phase, the system analyst seeks answers to these two questions

    1. Is the proposed system worthy pursuing?

    2. Is the proposed project worthy looking at?

    • Problem definition is performed by the senior members of the team with inputs from the customer, the sales department, market surveys and domain experts in the industry.

    This information is then used to plan the basic project approach and to conduct product feasibility study in the economical, operational, and technical areas.

    The scope of the project, constraints, budget and schedule is defined here

    • Problem definition is also called problem analysis; its the process of identifying the problem and finding out any constraints that may limit the solution

    • A feasibility study (preliminary investigation) is conducted at this stage; Feasibility study is an evaluation and analysis of the potential of a proposed project.

    It is based on extensive investigation and research to support the process of decision making.

  • Operational feasibility; establishes the extent to which the users are comfortable or happy with the proposed or new system
  • Schedule feasibility; establishes whether the development of the proposed system will be accomplished within the available time
  • Technical feasibility; establishes whether the technology available is sufficient or can be upgraded for the new system. It also seeks to find out whether the staff have relevant technical skills to develop and use the new system
  • Economic feasibility; establishes whether developing the new system is cost effective by analyzing all the costs and benefits of the proposed system. • After feasibility study has been conducted, a documentation is prepared to cover all the activities that took place.

    Information Gathering

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