## How Nested Loop works in C ?

The placing of one loop inside the body of another loop is called nesting . The outer loop takes control of the number of complete repetitions of the inner loop. for every iteration of the outer loop, the inner loop will be executed completely.

#include<stdio.h> int main() { int r,c; //counter variable declarations r=1; //init. of outer loop counter while ( r <= 3) // outer loop terminating condition { printf("\n-- OUTER LOOP NO. %d",r); c=1; //init. of inner loop counter while(c <= 5) //inner loop terminating condition { printf("\n\t-- INNER LOOP NO. %d",c); c=c+1; // counter incrementation for inner loop } r=r+1; // counter incrementation for outer loop } printf("\n-----------------------------------digitalpadm.com\n"); return 0; }

###### Download code : nested-loop-1.c (225 downloads)

In this example, Here total number of iterations of outer loop are 3 and inner loops are 5. for each iteration of outer loop, the inner loop will be executed 5 times. means when value of outer loop counter r is 1, c loop iterates from 1 to 5. for every value of r from 1 to 5 , c loops iterates completely.

**Output**

Note that, You can put any type of loop inside the body of another type of loop. as example, you can put a while loop inside the body of a for loop , or for loop inside do while and vice versa.

## Let’s see , How to print multiplication table using nested looping.

#include<stdio.h> int main() { int r,c,num; //counter variable declarations r=1; //init. of outer loop counter while ( r <= 10) // outer loop terminating condition { c=1; //init. of inner loop counter while(c <= 10) //inner loop terminating condition { num=r*c; printf(" %3d",num); c=c+1; // counter incrementation for inner loop } r=r+1; // counter incrementation for outer loop printf("\n"); } printf("\n-----------------------------------digitalpadm.com\n"); return 0; }

###### Download code: c-program-nested-loop-multiplication-table.c (232 downloads)

**Output**

Here , numbers of rows and cols are 10. the values of r varies from 1 to 10 as row numbers and for each value of r , the c varies from 1 to 10. hence the multiplication of r & c gives the table number.

as compared to nested loop structure using while loop , it is easier to implement using for loop

lets see , above example using for loop.

#include<stdio.h> int main() { int r,c,num; //counter variable declarations r=1; //init. of outer loop counter while ( r <= 10) // outer loop terminating condition { c=1; //init. of inner loop counter while(c <= 10) //inner loop terminating condition { num=r*c; printf(" %3d",num); c=c+1; // counter incrementation for inner loop } r=r+1; // counter incrementation for outer loop printf("\n"); } printf("\n-----------------------------------digitalpadm.com\n"); return 0; }

### Program to plot various triangular patterns using nested for Loop.

#include<stdio.h> int main() { int r,c,rows; //counter variable declarations r=1; //init. of outer loop counter rows=5; printf("\n\n"); for(r=1;r<=rows;r++) { for(c=r;c<=rows;c++) { printf("* "); } printf("\n"); } printf("\n"); printf("\n-----------------------------------digitalpadm.com\n"); return 0; }

###### Download code : nested-loop-pattern-triangle.c (226 downloads)

#### Explanation:

In this example, inner loop counter is initialized by outer loop counter value. so when the value of r is 1 , inner loop varies from 1 to 5, means 5 times so 5 * prints on screen.

when the value of r is 2 , inner loop varies from 2 to 5, means 4 times so 4 * prints on screen.

when the value of r is 3 , inner loop varies from 3 to 5, means 3 times so 3 * prints on screen. in same way when r is 5 , inner loop executes once so single * prints on screen.

#### Output:

#include<stdio.h> int main() { int r,c,rows; //counter variable declarations r=1; //init. of outer loop counter rows=10; printf("\n\n"); for(r=1;r<=rows;r++) { for(c=1;c<=r;c++) { printf("* "); } printf("\n"); } printf("\n"); printf("\n-----------------------------------digitalpadm.com\n"); return 0; }

###### Download code : nested-loop-triangle-pattern-2.c (198 downloads)

#### Output

In this example, inner loop counter varies from 1 to every outer loop counter value. so when the value of r is 1 , inner loop varies from 1 to 1, means 1 times so single * prints on screen.

when the value of r is 2 , inner loop varies from 1 to 2, means 2 times so 2 * prints on screen.

when the value of r is 3 , inner loop varies from 1 to 3, means 3 times so 3 * prints on screen. in same way when r is 5 , inner loop executes 5 times so 5 * prints on screen.

### C Program to Print Pyramid using Nested for Loop

#include<stdio.h> int main() { int r,c,k,rows; //counter variable declarations r=1; //init. of outer loop counter rows=10; printf("\n\n"); for(r=1;r<=rows;r++) { for(k=1;k<=rows-r;k++) { printf(" "); } for(c=1;c<=r;c++) { printf(" * "); } printf("\n"); } printf("\n"); printf("\n-----------------------------------digitalpadm.com\n"); return 0; }

###### Download Code : nested-loop-pyramid-pattern-3.c (219 downloads)

#### Explanation:

To print star in pyramid format, we need to insert a loop to add extra spaces before print star in a row. here loop with counter k varies from 1 to total number of rows minus row number. hence for first row ,total number of spaces are 10-1 as 9, & for second row it is 8 , third row 7 similarly for 9th row it is 1 and for 10th row its null.

#### Output:

#### Related programs on loops to learn more:

###### C Program Pascal Triangle Pattern Explanation

###### C Program – Loops Example – Fibonacci Series up to N terms

###### C Program –Loops Example -To Find Factorial of Number N