# Check if A Number is a Composite number or Not in C++

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## What is a Composite Number?

By definition, every integer greater than one is either a prime number or a composite number. A composite number is a positive integer number that is not prime number. In other words, it is a positive integer number which has at least one divisor other than 1 and itself. The composite numbers up to 20 are 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20.

The first 100 composite numbers are 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100, 102, 104, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 128, 129, 130, 132, 133

For example:
Input: 10
Output: yes, its Composite (Because 10 has divisors other than 1 and itself, for ex, 2 or 5).

Input: 5
Output: no, its not Composite (Because 5 is a prime number, as it has no other divisors other than 1 and itself). input: 23
output: no, its not Composite (Because 23 is a prime number, as it has no other divisors other than 1 and itself).

## Write a program to find Composite number between 0 to n in C++ :

### Code:

#include <iostream> using namespace std; bool isComposite(unsigned int i) { for( unsigned int j=2;j<i;j++) { if(i%j==0) { return true; } } return false; } int main() { unsigned int input = 1000; cout<<"Composite no. between 0 to "; cout<<input<<" are :\n\n"; for( unsigned int i=3;i<=input;i++) { if(isComposite(i)) { cout<<i<<" "; } } return 0; }