Multiplication By Addition

This code performs integer multiplication using repeated addition and subtraction. It handles both positive and negative values of ‘a’ and ‘b, ensuring that the result is accurate.

#include<stdio.h>
main()
{
 int a,b,i,multiplication=0;
 printf("Enter 1st value: ");
 scanf("%d",&a);
 printf("Enter 2nd value: ");
 scanf("%d",&b);
 if(b<0)
 {
  a=a+b;
  b=a-b;
  a=a-b;
 }
 if(a>=0)
 {
      for(i=1;i<=a;i++)
     multiplication+=b;
 }
 if(a<0)
 {
  for(i=a;i<=-1;i++)
  multiplication-=b;
 }
 printf("Multiplication=%d\n",multiplication);
}

Enter 1st value: 6
Enter 2nd value: 4
Multiplication=24

Explanation:

This C program calculates the product of two integers, ‘a’ and ‘b’, using repeated addition (for positive values of ‘a’) and repeated subtraction (for negative values of ‘a’). Here’s a step-by-step explanation of the code:

Header File:

• The program includes the standard C library header <stdio.h>. This header is required for input and output operations.

Main Function:

• The main function is the entry point of the program, where the execution begins.

Variable Declaration:

• The program declares the following integer variables:
• ‘a’ to store the first integer value.
• ‘b’ to store the second integer value.
• ‘i’ as a loop control variable.
• ‘multiplication’ to store the result of the multiplication.

User Input:

• The program prompts the user to enter two integer values ‘a’ and ‘b’ using printf and reads the input using scanf.

Adjustment for Negative ‘b’:

• The code checks if ‘b’ is negative (b < 0).
• If ‘b’ is negative, it performs a swap operation using simple addition and subtraction to ensure that ‘b’ is positive. This is done to simplify the multiplication calculation logic.

Multiplication Calculation:

• The program uses conditional statements to handle different cases:
• If ‘a’ is greater than or equal to 0, it enters a loop that runs ‘a’ times. In each iteration, ‘b’ is added to the ‘multiplication’ variable.
• If ‘a’ is less than 0, it enters a loop that runs from ‘a’ to -1. In each iteration, ‘b’ is subtracted from the ‘multiplication’ variable. This is essentially repeated subtraction.
• If ‘a’ is 0, the loop is not entered, and ‘multiplication’ remains 0.

Output:

• After calculating the product of ‘a’ and ‘b’, the program uses printf to display the result with the message “Multiplication=”.

End of Program:

• Once the result is printed, the program reaches the end of the main function, concluding the program’s execution.