Essential C Programming Exam Questions and Solutions

Store Fibonacci Series in an Array

Exam Source: 2024 Q6(b)

Note: fib[0]=0, fib[1]=1, fib[i] = fib[i-1] + fib[i-2] for i >= 2.

#include <stdio.h>

int main() {
    int n, i;
    printf("How many terms? ");
    scanf("%d", &n);
    int fib[n];
    fib[0] = 0;
    if (n > 1) fib[1] = 1;
    for (i = 2; i < n; i++)
        fib[i] = fib[i-1] + fib[i-2];
    printf("Fibonacci series: ");
    for (i = 0; i < n; i++)
        printf("%d ", fib[i]);
    return 0;
}

Dynamic Memory Allocation and Average Calculation

Exam Source: 2024 Q7(c) / 2025 Q6(a) — Repeated both years!

Note: malloc returns void*, cast to int*. Always free() after use. If malloc returns NULL, memory allocation failed.

#include <stdio.h>
#include <stdlib.h>

int main() {
    int n, i;
    printf("Enter size: ");
    scanf("%d", &n);
    int *arr = (int*) malloc(n * sizeof(int));
    if (arr == NULL) {
        printf("Memory allocation failed!\n");
        return 1;
    }
    for (i = 0; i < n; i++) {
        printf("arr[%d] = ", i);
        scanf("%d", &arr[i]);
    }
    float sum = 0;
    for (i = 0; i < n; i++) sum += arr[i];
    printf("Average = %.2f\n", sum / n);
    free(arr);
    return 0;
}

Recursive Factorial Function in C

Exam Source: 2025 Q6(c) — Very likely

Note: Base case: factorial(0)=1 and factorial(1)=1. Recursive step: n * factorial(n-1). Recursion uses more memory than iteration but results in cleaner code.

#include <stdio.h>

int factorial(int n) {
    if (n == 0 || n == 1)
        return 1;
    return n * factorial(n - 1);
}

int main() {
    int n;
    printf("Enter n: ");
    scanf("%d", &n);
    printf("%d! = %d\n", n, factorial(n));
    return 0;
}

Calculate the Sum of Digits of an Integer

Exam Source: 2025 Q4(b)

Note: Use the modulo operator (%) to extract the last digit and division (/ 10) to remove it. Repeat until the number becomes 0.

#include <stdio.h>

int main() {
    int n, sum = 0, digit;
    printf("Enter a number: ");
    scanf("%d", &n);
    if (n < 0) n = -n;
    while (n != 0) {
        digit = n % 10;
        sum += digit;
        n /= 10;
    }
    printf("Sum of digits = %d\n", sum);
    return 0;
}

C Structures: Student Marks and Minimum Score

Exam Source: 2025 Q8(b) — Very likely

Note: Structure members are accessed with a dot (.) for normal variables and an arrow (->) for pointers. Track the index of the minimum value while looping.

#include <stdio.h>

struct Student {
    char name[50];
    int marks;
};

int main() {
    struct Student s[5];
    int i, minIdx = 0;
    for (i = 0; i < 5; i++) {
        printf("Name: ");
        scanf("%s", s[i].name);
        printf("Marks: ");
        scanf("%d", &s[i].marks);
    }
    for (i = 1; i < 5; i++)
        if (s[i].marks < s[minIdx].marks)
            minIdx = i;
    printf("Minimum marks: %s (%d)\n", s[minIdx].name, s[minIdx].marks);
    return 0;
}

Copy File Contents Using Command Line Arguments

Exam Source: 2024 Q9(a) / 2025 Q9(a) — Repeated both years!

Note: argc is the argument count. argv[0] is the program name, argv[1] is the source file, and argv[2] is the destination file. Run as: ./program source.txt dest.txt

#include <stdio.h>

int main(int argc, char *argv[]) {
    if (argc != 3) {
        printf("Usage: program source dest\n");
        return 1;
    }
    FILE *src = fopen(argv[1], "r");
    FILE *dst = fopen(argv[2], "w");
    if (!src || !dst) {
        printf("File error!\n");
        return 1;
    }
    char ch;
    while ((ch = fgetc(src)) != EOF)
        fputc(ch, dst);
    fclose(src);
    fclose(dst);
    printf("File copied successfully!\n");
    return 0;
}