Repeat prime checking until user exits (do-while) Dry Run in C

Repeat prime checking until user exits (do-while) is an interactive C dry run visualizer from the Nested programs section. Study the source code, then use the execution controls to follow each step, variable update, highlighted line, and console output.

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Repeat prime checking until user exits (do-while) Program Code

#include <stdio.h>
int isPrime(int n) { int i;
    if(n < 2) return 0;
    for(i = 2; i * i <= n; i++)
        if(n % i == 0) return 0;
    return 1;
}

int main() {
    int num, choice;
    
    do {
        printf("\n=== Prime Number Checker ===\n");
        printf("Enter a number: ");
        scanf("%d", &num);
        
        if(isPrime(num))
            printf("%d is a PRIME number\n", num);
        else
            printf("%d is NOT a prime number\n", num);
        
        // Find next prime
        int next = num + 1;
        while(!isPrime(next)) next++;
        printf("Next prime after %d is %d\n", num, next);
        
        // Find previous prime
        int prev = num - 1;
        while(prev >= 2 && !isPrime(prev)) prev--;
        if(prev >= 2)
            printf("Previous prime before %d is %d\n", num, prev);
        
        printf("\nPress 1 to check another number, 0 to exit: ");
        scanf("%d", &choice);
        
    } while(choice == 1);
    
    printf("Thank you for using Prime Checker!\n");
    return 0;
}

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