7.1 The Program Development Life Cycle

(a) System:

A system is a collection of components that work together as parts of a mechanism or an interconnecting network with a set of rules or procedures to solve a problem.

(b) Computer System:

• A computer system is made up of software, data, hardware, communications and people.
• It is a set of integrated devices that input, process, output, communicate and store data and information.
• A computer system can be divided into a set of sub-systems.
• Each sub-system can be further divided into sub-systems and so on until each sub-system just performs a single action.

(a) System Development Life Cycle (SDLC):

System Development Life Cycle is an organisational process of developing and maintaining a system.

It helps in establishing a system project plan by giving an overall list of processes and sub-processes required in developing a system.

(b) Reasons why we need to develop a new system:

• The current system may no longer be suitable for its purpose.
• Technological developments may have made the current system redundant or outdated.
• The current system may be too inflexible or expensive to maintain.

1) Analysis

The analysis stage involves the process of investigation — a detailed study of the current system to identify the problems and collect the key elements required to develop a new, more efficient system.

It is done by abstraction and decomposition tools.

• Abstraction collects the essential elements required for the solution while eliminating any unnecessary details and information.
• Decomposition involves breaking down a complex problem into smaller, more manageable parts that can be solved individually.

2) Design

The design stage is the process of planning a new system to solve the problems identified and to meet the requirements collected at the analysis stage.

It is formally documented using structure diagrams, flowcharts and pseudocode, to show what is to be done, how each task is to be performed and how the tasks work together.

When the design stage is complete, the programmer should know what is to be done.

3) Coding

The coding stage is the process of writing the program using a suitable programming language.

Each module of the program is tested repeatedly to debug errors if any, amend codes if needed, and check if it meets all the requirements of the system.

4) Testing

The testing stage is the process of repeatedly running and testing the completed program using different sets of test data.

This ensures that all the tasks completed work together as specified in the program design and its output matches the expected results.

1. Abstraction

Abstraction collects the key elements required and discards any unnecessary details for the solution of the problem.

2. Decomposition

Decomposition breaks down a complex problem into smaller parts, which can then be subdivided into even smaller parts that can be solved easily.

1. Structure Diagram

A pictorial representation of top-down design in a hierarchical form.

It is an ordered way of designing a system, by breaking down a system into its sub-systems down to its lowest manageable levels in a tree-like structure.

It is constructed using squares to represent systems, and lines that connect them. The lines represent the connection between activities and sub-activities, as they are used in organisation charts.

2. Flowchart

A diagram that represents an algorithm, the work-flow or process.

It shows the steps to be carried out to solve a problem. It uses a variety of boxes and arrows to show the process to be done and the direction of flow of data.

3. Pseudocode

A method that describes the steps of an algorithm using English-like words and mathematical operators.

It is set out to look like a computer program without following the strict syntax or rules of any specific programming language.