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How to Write a program?

Introduction

A Program has a three major components:

  • Input Design
  • Business Logic
  • Output

To write a program measure the following facts:

What are the Inputs will be given?
What is the Business Logic?
What is the Output?

For example,let us write a program for adding two Integer Numbers.

#include<stdio.h>

//Empty Main Function
void main( )
{
......
......


Input Design

For this program we need two integer numbers for addition. And we declare  two variables named a,b as integer data type. 

void main( )
{
int a,b; 
......
}

And we need another variable named as c, which is used for storing  the result of the added numbers.

void main()
{
int a,b,c; 
......
}

And get the two numbers from the user interface. In C we use printf and scanf functions
that syntax:

printf("Enter two Numbers:");

The above  statement is used  for displaying user interface information.

scanf("%d%d",&a,&b);

scanf is used to get the information from user screen.

In the above statement the first %d get the integer value of the variable a and store the value of a in a's memory location itself (&a is denoting the a's Memory Area).

Then the, second %d get the integer value of the variable b and store the value of b in b's memory location itself ( &b is denoting the b's Memory Area).


void main()
{
int a,b,c; 
printf("Enter two Numbers:");
scanf("%d%d",&a,&b);
......
}

Business Logic

Here business logic is "adding two numbers". Business logic is doesn't affect any platforms,any languages it is most probably same think for all languages.

In this program, the two numbers a and b are added and stored in the variable  c. 
So, we write
c = a + b;

Now we get,

void main()
{
int a,b,c;
printf("Enter two Numbers:");
scanf("%d%d",&a,&b);
c = a + b;
......
}


Output Design

In C we use printf statement to show the output of the given program.
printf("Result :%d",c);

The above code prints Result : and %d replaces the c's Integer Value.

And  finally we get the following program in a full-fledged form, void main()
{
int a,b,c;
printf("Enter two Numbers:");
scanf("%d%d",&a,&b);
c = a + b;
printf("Result :%d",c);
}

References


R.G Dromy
How to Program