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Purpose of Program Planning

If your teacher asked you to solve an

arithmetic problem & you are not familiar

with the steps involved in solving the problem,

you will not be able to solve it.

The same principle applies to writing computer

programs also.

A programmer cannot write the instructions for acomputer to execute unless the programmer knows

how to solve the problem manually.

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Contd

If you know the steps for solving a problem but

while solving it, you forget to apply some of the

steps or you apply the steps in the wrong

sequences, you will get a wrong answer. While writing a computer program, if the programmer

leaves out some of the instructions for the computer or

writes the instructions in the wrong sequence, the

computer will produce a wrong answer.

So, to produce an effective computer program it is

compulsory to write every instruction in the correct

sequence.

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Contd

Therefore, program before learning how to

write a computer, we will first learn how to

plan its logic.

Program Planning Tools:-

Algorithms

Flowcharts

Pseudocodes

Decision Tables

Programs

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Algorithm

Refers to the logic of the program

It is a step by step description of how to arrive at a solution

of the given problem.

Basically, it is defined as a sequence of instructions that

when executed in the specified sequence, the desired results

are obtained.

Characteristicsof an algorithm: -

Each instruction should be precise & unambiguous.

Each instruction should be executed in a finite time.

One or more instructions should not be repeated infinitely. This

ensures that the algorithm will ultimately terminate.

After executing the instructions (when the algorithm terminates),

the desired results are obtained.

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Representation of Algorithms

As Flowcharts

As Pseudocodes

As programs

Note: - Any program is an algorithm, but the

reverse is not true.

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Flowcharts

It is a pictorial representation of an algorithm.

The process of drawing a flowchart for an

algorithm is called flowcharting. Uses boxes of different shapes to denotes

different types of instructions.

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Basic Flowchart Symbols

Terminal

Input / Output

Processing

Decision

Flow Lines

Connectors

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Flowcharting Rules

First chart the main line of logic, & then incorporate

details.

Maintain a consistent level of details for a given flowchart.

Dontchart every detail.

Use common statements that are easy to understand for

words within flowchart symbols.

Be consistent in using names & variables in the flowchart.

Go from left to right & top to bottom in constructing

flowcharts. Keep the flowchart as simple as possible. Crossing of flow

lines should be avoided.

If a new flowcharting page is needed, break the flowchart

at an i/o point. Use properly labeled connectors to link the

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Adv. & Disadv. of Flowcharts

Advantages : -

Better communication

Proper program Documentation

Efficient Coding

Systematic Debugging & Systematic Testing Disadvantages : -

Very time consuming & laborious to draw with proper

symbols & spacing especially for large complex

programs.

Any change/modifications in the program logic will use a

require a completely new flowchart.

No standards determining the amount of detail.

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Pseudo Code

Phrases written in ordinary natural language

that computer cantunderstand

Also known as Program Design Language It does not have any syntax rules for

formulating instructions

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Contd

Flowchart Pseudo code

Read NAME, BALANCE,

RATE

Compute INTEREST as

BALANCE x RATE

Write (Display) NAME and

INTEREST

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Adv & Disadv of Pseudocode

Advantages: -

As compared to a flowchart, converting a pseudocode to a PL is mucheasier.

As compared to a flowchart, it is easier to modify the pseudocode of

program logic when program modifications are necessary.

Writing of pseudocode involves much less time & effort than drawing

an equivalent flowchart.

Disadvantages: -

In case of pseudocode, a graphic representation of program logic is not

available.

No standard rules to follow in writing pseudocode. Communicationproblem occurs due to lack of standardization.

It is more difficult to follow the logic of pseudocode or write

pseudocode as compared to flowcharting.

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Decision tables

A table of contingencies for defining a

problem and actions to be taken

Single representation of relationship betweenconditions and actions

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Constructing a Decision Table

PART 1. FRAME THE PROBLEM. Identify the conditions (decision criteria). These are the factors that will

influence the decision.

E.g., We want to know the total cost of a students tuition. What

factors are important? Identify the range of values for each condition or criteria.

E.g. What are they for each factor identified above?

Identify all possible actions that can occur.

E.g. What types of calculations would be necessary?.

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Rules

Decision Table should be given a name at top

left.

Standardized language must be used consistently. Duplication of terms/meanings should be

eliminated.

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Thank You!!!