#include<stdio.h>

int main(){

    int num,i,count=0;
    printf("Enter a number: ");
    scanf("%d",&num);
    for(i=2;i<=num/2;i++){
        if(num%i==0){
         count++;
            break;
        }
    }
   if(count==0 && num!= 1)
        printf("%d is a prime number",num);
   else
      printf("%d is not a prime number",num);
   return 0;
}
Sample output:
Enter a number: 5
5 is a prime number

#include<stdio.h>

int main(){
    int num,i,count;
  
    for(num = 1;num<=100;num++){
         count = 0;

         for(i=2;i<=num/2;i++){
             if(num%i==0){
                 count++;
                 break;
             }
        }
        
         if(count==0 && num!= 1)
             printf("%d ",num);
    }
  
   return 0;
}
Output:
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

#include<stdio.h>

int main(){

    int num,i,count,n;
    printf("Enter max range: ");
    scanf("%d",&n);

    for(num = 1;num<=n;num++){

         count = 0;

         for(i=2;i<=num/2;i++){
             if(num%i==0){
                 count++;
                 break;
             }
        }
        
         if(count==0 && num!= 1)
             printf("%d ",num);
    }
  
   return 0;
}
Sample output:
Enter max range: 50
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47

#include<stdio.h>

int main(){

    int num,i,count,min,max;

     printf("Enter min range: ");
     scanf("%d",&min);

    printf("Enter max range: ");
    scanf("%d",&max);

    for(num = min;num<=max;num++){

         count = 0;

         for(i=2;i<=num/2;i++){
             if(num%i==0){
                 count++;
                 break;
             }
        }
        
         if(count==0 && num!= 1)
             printf("%d ",num);
    }
  
   return 0;
}
Alternate with while loop
#include<stdio.h>

int main(){

   int num,i,count,min,max;

printf("Enter min range: ");
    scanf("%d",&min);

    printf("Enter max range: ");
    scanf("%d",&max);

    num = min;
    while(num<=max){

         count = 0;
         i=2;

         while(i<=num/2){
             if(num%i==0){
                 count++;
                 break;
             }
             i++;
        }
        
         if(count==0 && num!= 1)
             printf("%d ",num);

         num++;
    }
  
   return 0;
}
Sample output:
Enter min range: 10
Enter max range: 50
11 13 17 19 23 29 31 37 41 43 47

#include<stdio.h>

int main(){

    int num,i,count,min,max,sum=0;

     printf("Enter min range: ");
     scanf("%d",&min);

    printf("Enter max range: ");
    scanf("%d",&max);

    for(num = min;num<=max;num++){

         count = 0;

         for(i=2;i<=num/2;i++){
             if(num%i==0){
                 count++;
                 break;
             }
        }
        
         if(count==0 && num!= 1)
             sum = sum + num;
    }

    printf("Sum of prime numbers is: %d ",sum);
  
   return 0;
}
Sample output:
Enter min range: 50
Enter max range: 100
Sum of prime numbers is: 732