1 Echo Number: Ask the user for their favorite whole number using scanf("%d", &num) and print: "Your lucky number is [num]!"

2 Age Calculator: Input the current year and the user's birth year as integers, calculate their age by subtraction, and print the result.

3 Simple Two-Number Math: Read two integers and . Print their sum, difference, product, and integer quotient.

4 Remainder Finder: Read two integers and use the modulus operator % to display the remainder when the first is divided by the second.

5 Rectangle Perimeter: Input the length and width of a room as integers; compute and display the perimeter ().

6. Temperature Converter: Take a temperature in Celsius as a float or double and convert it to Fahrenheit using $F = (C \times 9.0 / 5.0) + 32.0$. Print the result formatted to 2 decimal places (%.2f).

7. Discount Calculator: Input an item's original price (float) and a percentage discount (float). Calculate the savings and the final price to pay.

8. Circle Area & Circumference: Prompt for the radius as a decimal number. Define PI as 3.14159 and calculate both area ($\pi r^2$) and circumference ($2 \pi r$).

9. Average of Three Exam Scores: Prompt for three separate marks (decimals), calculate their average, and display it rounded to 1 decimal place.

10. Currency Conversion: Input an amount in Indian Rupees (INR) as a float, multiply it by an exchange rate (e.g., USD conversion rate), and print the foreign currency value.

11. Single Letter Echo: Ask the user to type a single character using scanf(" %c", &ch) and print: "You pressed key: [ch]".

12. Secret Code (ASCII Value): Read a single letter and print both the character and its numeric ASCII code (printf("%c has ASCII value %d", ch, ch)).

13. Next Letter in Line: Take a character input and print the next character in the alphabet simply by adding 1 (ch + 1).

14. Simple Upper-to-Lower: Read a capital letter and convert it to lowercase by adding 32 to its ASCII value (or using tolower()).

15. Grade Inspector: Take a single letter grade ('A', 'B', 'C') and print a custom encouraging message based on the letter.

16. Friendly Greeting: Declare a character array char name[50];, ask for the user's first name, and print "Welcome to C programming, [name]!"

17. Name Length Counter: Read a one-word name and count how many characters it contains using strlen() from <string.h> (or a simple loop until '\0').

18. Personalized ID Badge: Take a first name (string), age (int), and blood group letter (char), then print a neatly aligned 3-line ID card badge.

19. Grocery Bill Generator: Prompt for an item's name (string), quantity (int), and price per unit (float). Multiply to get the total and format a mini receipt.

20. Mini Mad-Libs Game: Ask for a friend's name (string), an animal (string), a lucky number (int), and a favorite decimal number (float). Assemble them into a funny 3-sentence story.

1. Echo Number

C

#include <stdio.h>

int main() {
    int num;

    printf("Enter your favorite whole number: ");
    scanf("%d", &num);

    printf("Your lucky number is %d!\n", num);
    return 0;
}

2. Age Calculator

C

#include <stdio.h>

int main() {
    int current_year, birth_year;

    printf("Enter current year: ");
    scanf("%d", &current_year);
    printf("Enter your birth year: ");
    scanf("%d", &birth_year);

    int age = current_year - birth_year;

    printf("You are %d years old.\n", age);
    return 0;
}

3. Simple Two-Number Math

C

#include <stdio.h>

int main() {
    int a, b;

    printf("Enter two integers: ");
    scanf("%d %d", &a, &b);

    printf("Sum: %d\n", a + b);
    printf("Difference: %d\n", a - b);
    printf("Product: %d\n", a * b);
    printf("Quotient: %d\n", a / b);
    return 0;
}

4. Remainder Finder

C

#include <stdio.h>

int main() {
    int num1, num2;

    printf("Enter two integers: ");
    scanf("%d %d", &num1, &num2);

    int remainder = num1 % num2;

    printf("The remainder when %d is divided by %d is: %d\n", num1, num2, remainder);
    return 0;
}

5. Rectangle Perimeter

C

#include <stdio.h>

int main() {
    int length, width;

    printf("Enter length and width of the room: ");
    scanf("%d %d", &length, &width);

    int perimeter = 2 * (length + width);

    printf("The perimeter of the room is: %d\n", perimeter);
    return 0;
}

Part 2: Floating-Point Math (float, %.2f, %.1f)

6. Temperature Converter

C

#include <stdio.h>

int main() {
    float celsius;

    printf("Enter temperature in Celsius: ");
    scanf("%f", &celsius);

    float fahrenheit = (celsius * 9.0 / 5.0) + 32.0;

    printf("%.2f C = %.2f F\n", celsius, fahrenheit);
    return 0;
}

7. Discount Calculator

C

#include <stdio.h>

int main() {
    float price, discount_pct;

    printf("Enter original price: ");
    scanf("%f", &price);
    printf("Enter discount percentage: ");
    scanf("%f", &discount_pct);

    float savings = price * (discount_pct / 100.0);
    float final_price = price - savings;

    printf("You save: $%.2f\n", savings);
    printf("Final price to pay: $%.2f\n", final_price);
    return 0;
}

8. Circle Area & Circumference

C

#include <stdio.h>

int main() {
    float radius;
    const float PI = 3.14159;

    printf("Enter the radius: ");
    scanf("%f", &radius);

    float area = PI * radius * radius;
    float circumference = 2 * PI * radius;

    printf("Area: %.2f\n", area);
    printf("Circumference: %.2f\n", circumference);
    return 0;
}

9. Average of Three Exam Scores

C

#include <stdio.h>

int main() {
    float m1, m2, m3;

    printf("Enter three exam scores: ");
    scanf("%f %f %f", &m1, &m2, &m3);

    float avg = (m1 + m2 + m3) / 3.0;

    printf("Average Score: %.1f\n", avg);
    return 0;
}

10. Currency Conversion

C

#include <stdio.h>

int main() {
    float inr;
    const float INR_TO_USD = 0.012; // Example exchange rate

    printf("Enter amount in Indian Rupees (INR): ");
    scanf("%f", &inr);

    float usd = inr * INR_TO_USD;

    printf("%.2f INR is approximately $%.2f USD\n", inr, usd);
    return 0;
}

Part 3: Characters & ASCII Values (char, %c)

11. Single Letter Echo

C

#include <stdio.h>

int main() {
    char ch;

    printf("Type a single character: ");
    // Note the space before %c to skip any lingering newline
    scanf(" %c", &ch);

    printf("You pressed key: %c\n", ch);
    return 0;
}

12. Secret Code (ASCII Value)

C

#include <stdio.h>

int main() {
    char ch;

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

    printf("%c has ASCII value %d\n", ch, ch);
    return 0;
}

13. Next Letter in Line

C

#include <stdio.h>

int main() {
    char ch;

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

    char next = ch + 1;

    printf("The next character is: %c\n", next);
    return 0;
}

14. Simple Upper-to-Lower

C

#include <stdio.h>

int main() {
    char upper;

    printf("Enter a capital letter: ");
    scanf(" %c", &upper);

    // Adding 32 converts uppercase ASCII to lowercase
    char lower = upper + 32;

    printf("Lowercase: %c\n", lower);
    return 0;
}

15. Grade Inspector

C

#include <stdio.h>

int main() {
    char grade;

    printf("Enter your grade (A, B, or C): ");
    scanf(" %c", &grade);

    if (grade == 'A' || grade == 'a') {
        printf("Outstanding work! Keep shining!\n");
    } else if (grade == 'B' || grade == 'b') {
        printf("Great job! You are doing very well!\n");
    } else if (grade == 'C' || grade == 'c') {
        printf("Good effort! Keep practicing and you will grow!\n");
    } else {
        printf("Keep working hard and learning!\n");
    }

    return 0;
}

Part 4: Strings & Mixed Mini-Projects (char[], %s, mixed types)

16. Friendly Greeting

C

#include <stdio.h>

int main() {
    char name[50];

    printf("Enter your first name: ");
    scanf("%s", name);

    printf("Welcome to C programming, %s!\n", name);
    return 0;
}

17. Name Length Counter

C

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

int main() {
    char name[50];

    printf("Enter a one-word name: ");
    scanf("%s", name);

    int length = strlen(name);

    printf("The name \"%s\" has %d characters.\n", name, length);
    return 0;
}

18. Personalized ID Badge

C

#include <stdio.h>

int main() {
    char name[50];
    int age;
    char blood_group;

    printf("Enter first name: ");
    scanf("%s", name);

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

    printf("Enter blood group letter (e.g. O, A, B): ");
    scanf(" %c", &blood_group);

    printf("\n=============================\n");
    printf("  NAME        : %s\n", name);
    printf("  AGE         : %d\n", age);
    printf("  BLOOD GROUP : %c+\n", blood_group);
    printf("=============================\n");

    return 0;
}

19. Grocery Bill Generator

C

#include <stdio.h>

int main() {
    char item[50];
    int qty;
    float price;

    printf("Enter item name: ");
    scanf("%s", item);

    printf("Enter quantity: ");
    scanf("%d", &qty);

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

    float total = qty * price;

    printf("\n--- GROCERY RECEIPT ---\n");
    printf("Item  : %s\n", item);
    printf("Qty   : %d\n", qty);
    printf("Price : $%.2f\n", price);
    printf("Total : $%.2f\n", total);
    printf("-----------------------\n");

    return 0;
}

20. Mini Mad-Libs Game

C

#include <stdio.h>

int main() {
    char friend_name[50];
    char animal[50];
    int lucky_num;
    float favorite_decimal;

    printf("Enter a friend's name: ");
    scanf("%s", friend_name);

    printf("Enter an animal: ");
    scanf("%s", animal);

    printf("Enter your lucky number: ");
    scanf("%d", &lucky_num);

    printf("Enter your favorite decimal number: ");
    scanf("%f", &favorite_decimal);

    printf("\n--- THE STORY ---\n");
    printf("One sunny afternoon, %s adopted a talking %s.\n", friend_name, animal);
    printf("Together, they found %d gold coins hidden under a rock.\n", lucky_num);
    printf("The %s happily munched on %.2f slices of watermelon and fell asleep!\n", animal, favorite_decimal);

    return 0;
}