C Programming Codes

💻 Check if String Starts with Vowel

#include <stdio.h>
#include <string.h>
#include <ctype.h>

int main() {
    char str[100];

    printf("Enter a string: ");
    scanf("%s", str);

    char firstChar = tolower(str[0]);

    if (firstChar == 'a' || firstChar == 'e' || firstChar == 'i' || firstChar == 'o' || firstChar == 'u') {
        printf("String starts with a vowel.n");
    } else {
        printf("String does not start with a vowel.n");
    }

    return 0;
}

📤 Output:

Input: apple
Output: String starts with a vowel.

Input: Banana
Output: String does not start with a vowel.

Input: Example
Output: String starts with a vowel.

Input: orange
Output: String starts with a vowel.

Input: umbrella
Output: String starts with a vowel.

Input: Test
Output: String does not start with a vowel.

💻 Check if Number is Palindrome

#include <stdio.h>

int main() {
    int n, reversedInteger = 0, remainder, originalInteger;

    printf("Enter an integer: ");
    scanf("%d", &n);

    originalInteger = n;

    while (n != 0) {
        remainder = n % 10;
        reversedInteger = reversedInteger * 10 + remainder;
        n /= 10;
    }

    if (originalInteger == reversedInteger)
        printf("%d is a palindrome.", originalInteger);
    else
        printf("%d is not a palindrome.", originalInteger);

    return 0;
}

📤 Output:

Input: 121
Output: 121 is a palindrome.

Input: 123
Output: 123 is not a palindrome.

Input: 3553
Output: 3553 is a palindrome.

Input: 12345
Output: 12345 is not a palindrome.

💻 Check if Character is Uppercase or Lowercase

#include <stdio.h>

int main() {
  char ch;

  printf("Enter a character: ");
  scanf(" %c", &ch);

  if (ch >= 'A' && ch <= 'Z') {
    printf("%c is an uppercase character.n", ch);
  } else if (ch >= 'a' && ch <= 'z') {
    printf("%c is a lowercase character.n", ch);
  } else {
    printf("%c is not an alphabet.n", ch);
  }

  return 0;
}

📤 Output:

Input: G
Output: Enter a character: G is an uppercase character.

Input: g
Output: Enter a character: g is a lowercase character.

Input: 5
Output: Enter a character: 5 is not an alphabet.

💻 Check if Triangle is Valid

#include <stdio.h>

int main() {
    int side1, side2, side3;

    printf("Enter the lengths of three sides of a triangle: ");
    scanf("%d %d %d", &side1, &side2, &side3);

    if (side1 + side2 > side3 && side1 + side3 > side2 && side2 + side3 > side1) {
        printf("Triangle is valid.n");
    } else {
        printf("Triangle is not valid.n");
    }

    return 0;
}

📤 Output:

Input: 3 4 5
Output: Triangle is valid.

Input: 1 2 5
Output: Triangle is not valid.

Input: 7 10 5
Output: Triangle is valid.

💻 Check if Number is Prime

#include <stdio.h>
#include <stdbool.h>

int main() {
  int num, i;
  bool isPrime = true;

  printf("Enter a positive integer: ");
  scanf("%d", &num);

  if (num <= 1) {
    isPrime = false;
  } else {
    for (i = 2; i <= num / 2; ++i) {
      if (num % i == 0) {
        isPrime = false;
        break; // Exit the loop if not prime
      }
    }
  }

  if (isPrime) {
    printf("%d is a prime number.n", num);
  } else {
    printf("%d is not a prime number.n", num);
  }

  return 0;
}

📤 Output:

Input: 7
Output: 7 is a prime number.

Input: 12
Output: 12 is not a prime number.

Input: 1
Output: 1 is not a prime number.

Input: 2
Output: 2 is a prime number.

Input: 0
Output: 0 is not a prime number.

Input: -5
Output: -5 is not a prime number.

💻 Check if Person is Eligible to Vote

#include <stdio.h>

int main() {
    int age;

    printf("Enter your age: ");
    scanf("%d", &age);

    if (age >= 18) {
        printf("You are eligible to vote!n");
    } else {
        printf("You are not eligible to vote yet.n");
    }

    return 0;
}

📤 Output:

Input: 25
Output: Enter your age: You are eligible to vote!

Input: 16
Output: Enter your age: You are not eligible to vote yet.

💻 Check Profit or Loss from Cost and Sell Price

#include <stdio.h>

int main() {
  float costPrice, sellingPrice, profit, loss;

  printf("Enter cost price: ");
  scanf("%f", &costPrice);

  printf("Enter selling price: ");
  scanf("%f", &sellingPrice);

  if (sellingPrice > costPrice) {
    profit = sellingPrice - costPrice;
    printf("Profit: %.2fn", profit);
  } else if (costPrice > sellingPrice) {
    loss = costPrice - sellingPrice;
    printf("Loss: %.2fn", loss);
  } else {
    printf("No profit, no loss.n");
  }

  return 0;
}

📤 Output:

Input: 100.00
Input: 120.00
Output: Profit: 20.00

Input: 100.00
Input: 80.00
Output: Loss: 20.00

Input: 100.00
Input: 100.00
Output: No profit, no loss.

💻 Check if Character is Alphabet or Digit

#include <stdio.h>

int main() {
    char ch;

    printf("Enter a character: ");
    scanf(" %c", &ch);

    if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')) {
        printf("%c is an alphabet.n", ch);
    } else if (ch >= '0' && ch <= '9') {
        printf("%c is a digit.n", ch);
    } else {
        printf("%c is not an alphabet or a digit.n", ch);
    }

    return 0;
}

📤 Output:

Input: A
Output: Enter a character: A is an alphabet.

Input: 5
Output: Enter a character: 5 is a digit.

Input: $
Output: Enter a character: $ is not an alphabet or a digit.

💻 Check if Number is Even or Odd

#include <stdio.h>

int main() {
    int number;

    printf("Enter an integer: ");
    scanf("%d", &number);

    if (number % 2 == 0) {
        printf("%d is even.n", number);
    } else {
        printf("%d is odd.n", number);
    }

    return 0;
}

📤 Output:

Input: 7
Output: 7 is odd.

Input: 12
Output: 12 is even.

Input: 0
Output: 0 is even.

Input: -5
Output: -5 is odd.

Input: -8
Output: -8 is even.

💻 Check if Number is Positive or Negative

#include <stdio.h>

int main() {
    int number;

    printf("Enter an integer: ");
    scanf("%d", &number);

    if (number > 0) {
        printf("The number is positive.n");
    } else if (number < 0) {
        printf("The number is negative.n");
    } else {
        printf("The number is zero.n");
    }

    return 0;
}

📤 Output:

Input: 5
Output: The number is positive.

Input: -3
Output: The number is negative.

Input: 0
Output: The number is zero.

🔧 Conditional Statements - if-else

🚀100 Days of LeetCode 2025 Challenge started Join below channel to be part of this challenge 🔗https://t.me/+utZsK17rSXRmZWQ1 ❌ Don't miss it guys, great channel in telegram for dsa

💻 Check if String is Empty

#include <stdio.h>
#include <string.h>

int main() {
    char str[100];
    printf("Enter a string: ");
    scanf("%s", str);

    if (strlen(str) == 0) {
        printf("The string is empty.n");
    } else {
        printf("The string is not empty.n");
    }

    return 0;
}

📤 Output:

Input: hello
Output: The string is not empty.

Input:
Output: The string is empty.

Input: abcdefghijklmnopqrstuvwxyz
Output: The string is not empty.

🚀100 Days of LeetCode 2025 Challenge started Join below channel to be part of this challenge 🔗https://t.me/+utZsK17rSXRmZWQ1 ❌ Don't miss it guys, great channel in telegram for dsa

💻 Check if Number is Divisible by 5

#include <stdio.h>

int main() {
    int number;

    printf("Enter an integer: ");
    scanf("%d", &number);

    if (number % 5 == 0) {
        printf("%d is divisible by 5n", number);
    } else {
        printf("%d is not divisible by 5n", number);
    }

    return 0;
}

📤 Output:

Input: 10
Output: 10 is divisible by 5

Input: 7
Output: 7 is not divisible by 5

💻 Check if Temperature is Freezing

#include <stdio.h>

int main() {
  int temperature;

  printf("Enter the temperature in Celsius: ");
  scanf("%d", &temperature);

  if (temperature <= 0) {
    printf("The temperature is freezing.n");
  } else {
    printf("The temperature is not freezing.n");
  }

  return 0;
}

📤 Output:

Input: -5
Output: The temperature is freezing.

Input: 25
Output: The temperature is not freezing.

Input: 0
Output: The temperature is freezing.

🚀100 Days of LeetCode 2025 Challenge started Join below channel to be part of this challenge 🔗https://t.me/+utZsK17rSXRmZWQ1

💻 Check if Year is Leap Year

#include <stdio.h>

int main() {
    int year;

    printf("Enter a year: ");
    scanf("%d", &year);

    if (year % 4 == 0) {
        if (year % 100 == 0) {
            if (year % 400 == 0) {
                printf("%d is a leap year.n", year);
            } else {
                printf("%d is not a leap year.n", year);
            }
        } else {
            printf("%d is a leap year.n", year);
        }
    } else {
        printf("%d is not a leap year.n", year);
    }

    return 0;
}

📤 Output:

Input: 2024
Output: 2024 is a leap year.

Input: 2023
Output: 2023 is not a leap year.

Input: 1900
Output: 1900 is not a leap year.

Input: 2000
Output: 2000 is a leap year.

💻 Check if Point is at Origin

#include <stdio.h>

int main() {
  int x, y;

  printf("Enter the x-coordinate: ");
  scanf("%d", &x);

  printf("Enter the y-coordinate: ");
  scanf("%d", &y);

  if (x == 0 && y == 0) {
    printf("The point is at the origin.n");
  } else {
    printf("The point is not at the origin.n");
  }

  return 0;
}

📤 Output:

Input: 0
Input: 0
Output: The point is at the origin.

Input: 1
Input: 2
Output: The point is not at the origin.