This C programming example is to check whether an entered number is prime or not. A prime number is a positive integer which is divisible only by 1 and itself. For example, 3,5,7,11,17 are few prime numbers. This program check for the prime number using the modulus(%) operator.

/* C program to check whether a given number is prime or not */ #include <stdio.h> int main() { int n, i, flag; printf("Enter a number \n"); scanf("%d", &n); if (n <= 1) { printf("Please enter a positive number.", n); return 0; } flag = 0; for (i = 2; i <= n / 2; i++) { if ((n % i) == 0) { flag = 1; break; } } if (flag == 0) { printf("%d is a prime number \n", n); } else { printf("%d is not a prime number \n", n); } return 0; }

Case 1: Enter a number 451 451 is not a prime number Case 2: Enter a number 79 79 is a prime number Case 3: Enter a number -12 Please enter a positive number.

1. The program accept a positive integer using the scanf function. If the number entered by the user is negative, it prompt the user to enter a positive number. 2. To check for the prime number, modulus operator is used which returns the remainder after dividing the entered number with each number up to n/2 (starting from 2). 3. If the remainder comes out zero in any case, that means the number is not prime and the variable flag is set to 1 and for loop is existed. Otherwise the value of flag remains 0. 4. Depending on the value of variable flag, message is printed on the screen using if-else statement.

Questions from Previous year GATE question papers

UGC NET Previous year questions and practice sets

Attempt a small test to analyze your preparation level. This GATE exam includes questions from previous year GATE papers.

Practice test for UGC NET Computer Science Paper. The questions asked in this NET practice paper are from various previous year papers.