Saturday, 8 May 2021

Algorithm - Key features of algorithm

 According to the dictionary, algorithm can be represented by “A process or set of rules to be followed in calculation or other problem solving operations, especially a computer”.


An algorithm is a finite set of instructions to accomplish a particular task in given problem.

Before writing a program for solving a problem it is better to write step by step process for solving it. This step by step process is called an algorithm.

Knuth (1968-1973) has given a list of five programming rules that are widely accepted as requirements

for an algorithm.

Finiteness: an algorithm must always terminate a finite number of steps.

Definiteness: Each step of an algorithm must be preciously defined the action to be carried out must be clear.

Input: Quantities which are given to it initially before the algorithm begins these inputs are taken from specified steps of objects.

Output: Quantities which have a specified relation to input.

Effectiveness: All of the operations to be performed in the algorithm must be sufficiently basic that they can in principle, by alone exactly and in a finite length of time by a man using paper and pencil.

Key features / various steps in algorithm development:

An algorithm has a finite number of steps may involve decision making and repetition. Broadly speaking an algorithm uses three control structures namely sequence, decision, and repetition.


Sequence means that each step of the algorithm is executed in the specified order.

Example: Algorithm to add two numbers.

Step1: start

Step2: read two numbers as a, b

Step3: set c=a+b;

Step4: print c

Step5: end  


Decision statements are used when the execution of a process depends on the outcome of some conditions. A condition is any statement that may evaluate either to a true value or false value. A decision statement can be stated using if..else construct in the following manner.

If condition

Then statement 1


The statement 2

Example: algorithm to check the equality of two numbers.

Step1: read two numbers as a, b

Step2: if a=b

Then print “two numbers are equal”


Print “two numbers are not equal”

Step3: end


Repetition which involves executing one or more steps for a number of time, can be implemented using construction such as while, do-while, for loops.


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