Program to Print the Multiplication Table in C

Here's a program to print multiplication of first n numbers in C programming language with proper explanation. Here n is a natural number describing the number up to which tables need to be printed.

# include <stdio.h> 
# include <conio.h> 
void main() 
{ 
 int r, c, y, n ; 
 clrscr() ; 
 r = 1 ; 
 printf("Enter a number up to which you want tables: ");
 scanf("%d", &n);
 printf("\n\nThe multiplication table for first %d numbers is :\n\n", n) ; 
 do 
 { 
  c = 1 ; 
  do 
  { 
   y = r * c ; 
   printf("%5d", y) ; 
   c = c + 1 ; 
  } while(c <= 10) ; 
  printf("\n\n") ; 
  r = r + 1 ; 
 } while(r <= n) ; 
 getch() ; 
}

Output of above program is

Enter a number up to which you want tables:  5

The multiplication table for first 5 numbers is :
                                                     
    1    2    3    4    5    6    7    8    9   10   
                                                     
    2    4    6    8   10   12   14   16   18   20   
                                                     
    3    6    9   12   15   18   21   24   27   30   
                                                     
    4    8   12   16   20   24   28   32   36   40   
                                                     
    5   10   15   20   25   30   35   40   45   50   

Explanation of above program 

Just like any other C program, first we include all the necessary header files and defines a main() function. Now in this example, we're displaying a multiplication table of first n numbers and we are displaying it in a grid form (like a matrix see the output). In order to display the output like that we have to use two loops also called as nested loops or loop within loop. So here we are using two do-while loops (any other loop will work fine).

Here we declared four integer variables - c, r, n and y. First lets understand what is the need of each variable.

• c - Its value ranges from 1 - 10. It is used as one operand to calculate the multiplication. Its value resets to 1 after a multiplication table of a particular number is calculated.
• n - It is a number entered by the user showing up to what number user wants the table calculation. If user enters 5 the table up to first 5 number will be displayed.
• r - It is the other operand in the calculation of multiplication. Its value ranges from 1 to n. It is incremented after a multiplication table of a particular number is displayed.
• y - It is a temporary variable and is used to hold each multiplication value and then that value is displayed.

Getting back to the explanation,  first value of r is set to 1 (for calculation of 1's table). Then user is prompt to enter a number up to which tables are displayed. Then comes the nested do while loops. Inside first do while loop, we first set value of c to 1 and then we write the second do while loop. In the inner do while loop, we calculate the multiplication and stores it in y with this expression

y = r * c;

Next we print the value of y and increment c by 1. Now we check if c <= 10 and if it is then we continue inside the inner do while loop. But when c > 10 we come out of the inner loop and increment r by 1 (to start working on next number) and checks if r  <= n. When r > n we terminate both the loops and hence terminate the execution of our program.

What does %5d mean?

If you notice inside printf() (line 17), you'll see %5d, now what does it mean? It means that you want an integer to be printed (%d) but with a padding of 5 (%5d). In other words, every number will be printed in a space of a 5 digit long number. If you look at the output you'll see that there's a space between every number. To see for yourself try to change the value to some other integer and based on that space between integers will increase or decrease.