Introduction

 

Programming as an Art Form

When programming emerged as an activity some forty years ago, the main preoccupation was with the correctness of the solution. Precisely how that solution was derived was very much subordinate to the actual solution itself.

The design tool that emerged from this period was the flowchart. Flowcharts are a diagrammatic representation of the flow of logic within a program or within an individual process. To some extent, they provided a means of depicting the program structure, but their main concern as with the logic flow. This reflected the contemporary view that programming was mainly concerned with logic.

Structured programming

Structured programming was developed during the 1950s after Edger Dijiksta’s insightful comments into the harmful nature of the GO TO statement. Dijiksta and others subsequently created a set of acceptable structures in programming that would enable development without GO TO statements.

The structured programming uses three control constructs namely:

·         Sequence

·         Selection

·         Repetition

These structures produced programs that were easier to read by humans easier to debug and easier to test.

Object Oriented Programming

Object – oriented programming (OOP) is an emerging major programming paradigm. Much of its approach to program and system design is owed to concepts which also gave rest to structured programming. An object is a particular instance of a class and consists, essentially, of data which defines its characteristics and current status together with procedures, or ‘methods’, which operate on the object.

For example, an object may be a bank account possessing data items which record the name and address of its owner and its current balance. It may have associated methods which allow its creation, deletion and amendment with deposits and withdrawals.

1.1.1.      Tools for Program Design

Over the years, in search for an optimum means of providing the precision needed for designing the solution to a problem, a number of design tools have emerged. The common aim is to remove the expression of the solution from the ‘plain language’ we might use in describing it to another person. ‘Plain’ – spoken or written language is often not plain at all. It is full of imprecision and ambiguities. It often leaves many things unsaid, relying on the ‘common sense’ of the listener and the reader.

The notation used for algorithm specification must conform to a basic set of criteria:

It must be concise – we must be able to describe the solution to a problem without writing multiple pages of text.

It must be unambiguous – the description og the procedure must not be open to alternative interpretations. We must remember that the algorithm will be executed by a machine which has no ‘common sense’ or inbuilt knowledge of the nature of the problem.

It must be capable of machine execution – the actions described must be capable of translation into precise, machine – executable operations. This precludes such statements as “choose the best candidate”. If this were the object of the operation, the steps involved in evaluating the exact criteria for what constituted “best” must be clearly set out.

It must promote elegance in the solution – the tool must prevent the programmer from using practices at the design stage which leads to poor programming style during implementation. The selection of an appropriate design tool has a great influence on the quality of the ultimate program. A good design tool will lead to programs which are elegant in their design, accurate in their operation and easy to amend and enhance over a long period of time. Conversely, a poor design tool will promote not of these criteria.

7.1.    Flowcharts

A flowchart is a diagrammatic representation of the processes involved in arriving at a solution to a problem. While many symbols are included in its notation, the. Most important are:

 

Process or operation

Decision

Termination                               Yes                         Terminator

Flow of logic

Connector

Input / Output

Flow Chart – 2 Selection – Flowchart to input 2 numbers and thereafter evaluate and display the maximum value.

START

Input A, B

Max = A

Print Max

STOP

Max = B

A > B ?

No

Yes

Briefly describe the following structured control constructs.   Sequence –     Selection –     Iteration –

Flow Chart – 1 Sequence – Flowchart to input two numbers and thereafter calculate and display the average.

START

Input A, B

Avg =(A+B)/2

Print Avg

STOP