PROGRAM DEVELOPMENT (SS2 3RD TERM)

PROGRAM DEVELOPMENT

Definition of a Program

A computer program can be defined as an organized list of instruction (issued to the computer to perform a particular task) that cause it behave in a predetermined manner when executed. Programs are written in computer

programming languages.

What is a program?

A computer program can be defined as a collection of instructions that performs a specific task when executed by a computer.

Characteristics of a good program

Every good program must have the following characteristics:

1.            Accuracy                 

2.            Simplicity                

3.            Readability

4.            Maintainability 

5.            Efficiency

6.            Feasibility

7.            Generality

8.            Clarity

9.            Modularity

10.        Transferability

11.        Re-usability   

12.        Extensibility

 Brief descriptions on the Characteristics of a good program

1. Accuracy: a program should be sufficiently accurate to get the desired results.

2. Simplicity: a program logic should be simple and uncomplicated.

3. Readability: The program must be easy for any programmer to read and understand.

4. Maintainability: a good program must be easy to update.

5. Efficiency: program must be designed to use the least amount of primary storage.

6.       Feasibility: a program must be planned for maximum testing, ease and debugging convenience.

7.      Generality: a program must be able to process different kinds of data.

8.      Clarity: Every good and tested program must be clear, straight forward and easy to understand.

9.       Modularity: every good program must be built in blocks or modules.

10.     Transferability: a good program must be machine independent.

11.     Re-usability: program must be written with codes that can be used in another project.

12.     Extensibility: a program must be designed in a way that one can add or remove elements from the program without disturbing the structure of the program.

Precautions to be taken when writing a program:

1.       Patience:   Do no rush. Be careful, stable and patient when writing programs

2.       Step Following: No step should be skipped.

3.       Execution Order: The order to execute programs must be followed sequentially.

Stages in Program Development

Before the coding of a good program, there must be a proper planning and steps on how the problem or program will be solved. The steps/stages include the following:

PROGRAM DEVELOPMENT STEPS

1.       PROBLEM DEFINITION: This involves a clear, unambiguous understanding of the problem to be solved by the program

2.       PROBLEM ANALYSIS: This involves determining how the problem will be solved and the required input and output

3.       SOLUTION PLANNING: This involves writing the algorithm and plotting the program flowchart

4.       DESK CHECKING: This is a manual (non-computerised) technique for checking the logic of an algorithm.

5.       PROGRAM CODING: This is the actual writing of the program using a chosen programming language. e.g. Basic, VBasic, FORTRAN, Pascal, COBOL etc.

6.       PROGRAM COMPILATION: This involves transforming the source code to machine executable form.

·        logical analysis

·        syntactic analysis

·        code generation

·        code optimization

7.       PROGRAM TESTING/DEBUGGING: This involves finding and correcting program errors.

8.       PROGRAM DOCUMENTATION: This involves the production of documentation describing how the program works.

Documentation is the last stage of system development. A properly documented program can easily be used again when needed.

The techniques used in documentation

1. flowchart

2. comment

3. memory map

4. parameter and definition list

Program running

This is the actual running or execution of the program with the compiler or interpreter so as to check if the desired output is generated.

Maintenance

It is the process of updating or amending a previously written program for current use.

 

INTERPRETED PROGRAMMING LANGUAGES: An interpreted programming language execute instructions directly one line at a time, without previously compiling a program into machine-language instructions

EXAMPLES:

1.       BASIC

2.       PERL

3.       PYTHON

4.       PHP

Interpreter characteristics:

1.       Relatively little time is spent analyzing and processing the program

2.       The resulting code is some sort of intermediate code

3.       The resulting code is interpreted by another program

4.       Program execution is relatively slow

COMPILED PROGRAMMING LANGUAGES: A compiled programming language converts entire source codes to machine language instructions before execution.

EXAMPLES

1.       C

2.       C++

3.       COBOL

4.       FORTRAN

Compiler characteristics;

1.       Spends a lot of time analyzing and processing the program

2.       The resulting executable is some form of machine – specific binary code.

3.       The computer hardware interprets (executes) the resulting code program

4.       Execution is fast