# C++ nested loops

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A loop can be nested inside of another loop. C++ allows at least 256 levels of nesting.

## Syntax:

The syntax for a **nested for loop** statement in C++ is as follows:

for ( init; condition; increment ) { for ( init; condition; increment ) { statement(s); } statement(s); // you can put more statements. }

The syntax for a **nested while loop** statement in C++ is as follows:

while(condition) { while(condition) { statement(s); } statement(s); // you can put more statements. }

The syntax for a **nested do...while loop** statement in C++ is as follows:

do { statement(s); // you can put more statements. do { statement(s); }while( condition ); }while( condition );

## Example:

The following program uses a nested for loop to find the prime numbers from 2 to 100:

#include <iostream> using namespace std; int main () { int i, j; for(i=2; i<100; i++) { for(j=2; j <= (i/j); j++) if(!(i%j)) break; // if factor found, not prime if(j > (i/j)) cout << i << " is prime\n"; } return 0; }

This would produce the following result:

2 is prime 3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime 53 is prime 59 is prime 61 is prime 67 is prime 71 is prime 73 is prime 79 is prime 83 is prime 89 is prime 97 is prime

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