Unique C Programs for Problem Solving: From Basics to Advanced

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Last Updated on: 30th Jul 2025 00:24:17 AM

Welcome to an exciting journey through unique and practical C programs designed for beginer students .These programs cover a wide range of topics—basics, arrays, strings, pointers, structures, file handling, and dynamic memory allocation—progressing from beginner-friendly to advanced, real-life applications. Each program is interactive (using scanf and fgets), includes a description, code, sample output, and a clear explanation, making learning fun and engaging. Whether you’re calculating tips, managing a library, or simulating a bank, these programs will spark creativity and sharpen your C skills. Let’s dive in and solve some problems!

 

Table of Contents

1. Basic Programs (1–10)

2. Arrays and Strings (11–20)

3. Pointers (21–30)

4. Structures and Unions (31–40)

5. File Handling (41–45)

6. Dynamic Memory Allocation (46–50)

 

1. Basic Programs

 

1. Calculate Restaurant Tip

Description: Calculate a restaurant bill’s tip based on user input for the bill amount and tip percentage.

#include <stdio.h>
int main() {
    float bill, tip_percent, tip;
    printf("Enter bill amount: $");
    scanf("%f", &bill);
    printf("Enter tip percentage: ");
    scanf("%f", &tip_percent);
    tip = bill * (tip_percent / 100);
    printf("Tip: $%.2f\n", tip);
    printf("Total: $%.2f\n", bill + tip);
    return 0;
}

 

Output (Input: 50, 15):

Enter bill amount: $50
Enter tip percentage: 15
Tip: $7.50
Total: $57.50

 

Explanation: Takes bill and tip percentage, calculates the tip, and adds it to the bill. Uses scanf for input and %.2f for formatted output.

 

2. Check Leap Year

Description: Determine if a user-entered year is a leap year.

#include <stdio.h>
int main() {
    int year;
    printf("Enter year: ");
    scanf("%d", &year);
    if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) {
        printf("%d is a leap year.\n", year);
    } else {
        printf("%d is not a leap year.\n", year);
    }
    return 0;
}

Output (Input: 2024):

Enter year: 2024
2024 is a leap year.

 

Explanation: Checks if the year is divisible by 4 and not 100, or by 400, to determine leap year status.

 

3. Swap Two Numbers

Description: Swap two user-entered numbers using a temporary variable.

#include <stdio.h>
int main() {
    int a, b, temp;
    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);
    printf("Before swap: a = %d, b = %d\n", a, b);
    temp = a;
    a = b;
    b = temp;
    printf("After swap: a = %d, b = %d\n", a, b);
    return 0;
}

 

Output (Input: 5, 10):

Enter two numbers: 5 10
Before swap: a = 5, b = 10
After swap: a = 10, b = 5

Explanation: Uses a temporary variable to swap two numbers, demonstrating basic variable manipulation.

 

4. Factorial of a Number

Description: Calculate the factorial of a user-entered number.

#include <stdio.h>
int main() {
    int n;
    unsigned long fact = 1;
    printf("Enter a number: ");
    scanf("%d", &n);
    if (n < 0) {
        printf("Factorial is not defined for negative numbers.\n");
    } else {
        for (int i = 1; i <= n; i++) {
            fact *= i;
        }
        printf("Factorial of %d = %lu\n", n, fact);
    }
    return 0;
}

Output (Input: 5):

Enter a number: 5
Factorial of 5 = 120

Explanation: Uses a loop to multiply numbers from 1 to n. Handles negative input with a check.

 

5. Fibonacci Sequence

Description: Print the Fibonacci sequence up to a user-specified number of terms.

#include <stdio.h>
int main() {
    int n, first = 0, second = 1, next;
    printf("Enter number of terms: ");
    scanf("%d", &n);
    printf("Fibonacci Sequence: ");
    for (int i = 0; i < n; i++) {
        if (i <= 1) {
            next = i;
        } else {
            next = first + second;
            first = second;
            second = next;
        }
        printf("%d ", next);
    }
    printf("\n");
    return 0;
}

 

Output (Input: 6):

Enter number of terms: 6
Fibonacci Sequence: 0 1 1 2 3 5

Explanation: Generates Fibonacci numbers by adding the previous two terms, printing n terms.

 

6. Check Prime Number

Description: Check if a user-entered number is prime.

#include <stdio.h>
int main() {
    int n, isPrime = 1;
    printf("Enter a number: ");
    scanf("%d", &n);
    if (n <= 1) {
        isPrime = 0;
    } else {
        for (int i = 2; i * i <= n; i++) {
            if (n % i == 0) {
                isPrime = 0;
                break;
            }
        }
    }
    printf("%d is %sprime.\n", n, isPrime ? "" : "not ");
    return 0;
}

 

Output (Input: 17):

Enter a number: 17
17 is prime.

Explanation: Checks divisibility up to the square root of n to determine if it’s prime.

 

7. Reverse a Number

Description: Reverse the digits of a user-entered number.

#include <stdio.h>
int main() {
    int n, reversed = 0,remainder;
    printf("Enter a number: ");
    scanf("%d", &n);
    while (n > 0) {
        remainder = n % 10;  // Get the last digit
        reverse = reverse * 10 + remainder;
        n /= 10;
    }
    printf("Reversed number: %d\n", reversed);
    return 0;
}

 

Output (Input: 1234):

Enter a number: 1234
Reversed number: 4321

Explanation: Extracts digits using modulo and builds the reversed number.

 

8. Palindrome Number

Description: Check if a user-entered number is a palindrome.

#include <stdio.h>

int main() {
    int num, reverse = 0, remainder, original;

    // Taking input for the number
    printf("Enter a number: ");
    scanf("%d", &num);

    // Store the original number for comparison later
    original = num;

    // Reverse the number
    while (num != 0) {
        remainder = num % 10;  // Get the last digit
        reverse = reverse * 10 + remainder;  // Build the reversed number
        num /= 10;  // Remove the last digit
    }

    // Check if the original number is equal to the reversed number
    if (original == reverse) {
        printf("%d is a palindrome.\n", original);
    } else {
        printf("%d is not a palindrome.\n", original);
    }

    return 0;
}

 

Output (Input: 1221):

Enter a number: 1221
1221 is a palindrome

Explanation: Reverses the number and compares it with the original to check for palindrome.

 

9. Sum of Digits

Description: Calculate the sum of digits of a user-entered number.

#include <stdio.h>
int main() {
    int n, sum = 0;
    printf("Enter a number: ");
    scanf("%d", &n);
    while (n > 0) {
        sum += n % 10;
        n /= 10;
    }
    printf("Sum of digits: %d\n", sum);
    return 0;
}

 

Output (Input: 123):

Enter a number: 123
Sum of digits: 6

Explanation: Extracts each digit using modulo and adds to the sum.

 

10. Simple Interest Calculator

Description: Calculate simple interest based on principal, rate, and time.

#include <stdio.h>
int main() {
    float principal, rate, time, interest;
    printf("Enter principal, rate, time: ");
    scanf("%f %f %f", &principal, &rate, &time);
    interest = (principal * rate * time) / 100;
    printf("Simple Interest: $%.2f\n", interest);
    return 0;
}

 

Output (Input: 1000, 5, 2):

Enter principal, rate, time: 1000 5 2
Simple Interest: $100.00

Explanation: Applies the simple interest formula: (principal * rate * time) / 100.

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