Learn C - 16 Code Examples & CST Typing Practice Test

C is a general-purpose, procedural programming language that provides low-level access to memory, efficient performance, and a foundation for system and application software development.

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Hello World in C Sum of First N Numbers Factorial of a Number Check Even or Odd Reverse a Number Find Largest of Three Numbers Swap Two Numbers Fibonacci Series Palindrome Check Prime Number Check Print Personal Information Structure of C Program Syntax Error Example Logical Error Example Runtime Error Example Comments and Documentation Example

Learn C with Real Code Examples

Updated Nov 27, 2025

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Code Sample Descriptions

Hello World in C

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    int numbers[] = {1, 2, 3, 4, 5};

    int sum = 0;

    for (int i = 0; i < 5; i++) {
        sum += numbers[i];
    }

    printf("Sum: %d\n", sum);
    return 0;

}

A basic C program demonstrating array manipulation, loops, and printf. Calculates sum of numbers in an array.

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Sum of First N Numbers

#include <stdio.h>

int main() {
    int n = 10, sum = 0;
    for (int i = 1; i <= n; i++) {
        sum += i;
    }
    printf("Sum: %d\n", sum);
    return 0;
}

Calculates the sum of first N natural numbers using a for loop and demonstrates basic arithmetic operations.

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Factorial of a Number

#include <stdio.h>

int main() {
    int n = 5, fact = 1;

    for (int i = 1; i <= n; i++) {
        fact *= i;

    }

    printf("Factorial: %d\n", fact);

    return 0;

}

Calculates factorial of a number using iterative multiplication. Demonstrates loops and basic math operations.

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Check Even or Odd

#include <stdio.h>

int main() {
    int n = 7;

    if (n % 2 == 0)

        printf("%d is Even\n", n);

    else

        printf("%d is Odd\n", n);

    return 0;

}

Uses modulo operator to determine if a number is even or odd. Basic conditional logic demonstration.

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Reverse a Number

#include <stdio.h>

int main() {
    int n = 1234, rev = 0;

    while (n != 0) {
        rev = rev * 10 + n % 10;

        n /= 10;

    }

    printf("Reversed: %d\n", rev);

    return 0;

}

Reverses a number using modulo and division operations. Shows digit manipulation and while loop usage.

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Find Largest of Three Numbers

#include <stdio.h>

int main() {
    int a = 10, b = 20, c = 15;

    if (a >= b && a >= c)

        printf("Largest: %d\n", a);

    else if (b >= a && b >= c)

        printf("Largest: %d\n", b);

    else

        printf("Largest: %d\n", c);

    return 0;

}

Finds the largest number among three using nested if-else statements. Demonstrates comparison operations.

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Swap Two Numbers

#include <stdio.h>

int main() {
    int a = 5, b = 10, temp;

    temp = a;

    a = b;

    b = temp;

    printf("a = %d, b = %d\n", a, b);

    return 0;

}

Demonstrates swapping two numbers using a temporary variable. Basic variable manipulation example.

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Fibonacci Series

#include <stdio.h>

int main() {
    int n = 10, a = 0, b = 1, c;

    printf("%d %d ", a, b);

    for (int i = 2; i < n; i++) {
        c = a + b;

        printf("%d ", c);

        a = b;

        b = c;

    }

    return 0;

}

Generates Fibonacci sequence using iteration. Shows sequence generation and variable updates.

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Palindrome Check

#include <stdio.h>

int main() {
    int n = 121, orig = n, rev = 0;

    while (n != 0) {
        rev = rev * 10 + n % 10;

        n /= 10;

    }

    if (orig == rev)

        printf("Palindrome\n");

    else

        printf("Not Palindrome\n");

    return 0;

}

Checks if a number reads the same forwards and backwards. Uses digit extraction and reversal.

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Prime Number Check

#include <stdio.h>

int main() {
    int n = 29, isPrime = 1;

    for (int i = 2; i <= n / 2; i++) {
        if (n % i == 0) {
        isPrime = 0;

        break;

        }

    }

    if (isPrime)

        printf("%d is Prime\n", n);

    else

        printf("%d is Not Prime\n", n);

    return 0;

}

Determines if a number is prime by checking divisibility up to square root. Shows optimization in prime checking.

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Print Personal Information

#include <stdio.h>

int main() {
    printf("Name: Saurav\n");
    printf("Address: Nepal\n");
    printf("Age: 21\n");
    return 0;
}

Prints personal details like name, address, and age using printf statements.

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Structure of C Program

#include <stdio.h>

int main() {
    printf("This is a basic C program\n");
    return 0;
}

Demonstrates the basic structure of a C program.

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Syntax Error Example

#include <stdio.h>

int main() {
    int a = 10;
    printf("Value of a: %d\n", a);
    return 0;
}

Contains a syntax error for debugging practice.

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Logical Error Example

#include <stdio.h>

int main() {
    int l = 10, b = 5;
    int area = l + b;
    printf("Area = %d\n", area);
    return 0;
}

Program runs but gives incorrect output due to logical error.

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Runtime Error Example

#include <stdio.h>

int main() {
    int a = 10, b = 0;
    int c = a / b;
    printf("Result = %d\n", c);
    return 0;
}

Demonstrates runtime error caused by division by zero.

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Comments and Documentation Example

#include <stdio.h>

/*
    Program Name: Simple Addition
    Description: Adds two integers
    Author: Student
*/

int main() {
    int a = 5, b = 7;
    int sum = a + b;
    printf("Sum = %d\n", sum);
    return 0;
}

Demonstrates use of comments and documentation in C.

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Frequently Asked Questions about C

What is C?

C is a general-purpose, procedural programming language that provides low-level access to memory, efficient performance, and a foundation for system and application software development.

What are the primary use cases for C?

Operating system kernels (e.g., Linux, Windows). Embedded systems and microcontrollers. Device drivers and hardware interfaces. Compilers, interpreters, and runtime systems. High-performance computing and real-time applications

What are the strengths of C?

High performance and low overhead. Portable across platforms. Fine control over system resources. Large ecosystem and mature tooling. Foundation for many other programming languages

What are the limitations of C?

No built-in memory safety (manual management required). Lacks object-oriented features. Limited standard library compared to modern languages. Error handling via return codes, no exceptions. Steeper learning curve for beginners due to pointers and memory

How can I practice C typing speed?

CodeSpeedTest offers 16+ real C code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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Code Sample Descriptions

Hello World in C

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    int numbers[] = {1, 2, 3, 4, 5};

    int sum = 0;

    for (int i = 0; i < 5; i++) {
        sum += numbers[i];
    }

    printf("Sum: %d\n", sum);
    return 0;

}

A basic C program demonstrating array manipulation, loops, and printf. Calculates sum of numbers in an array.

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Sum of First N Numbers

#include <stdio.h>

int main() {
    int n = 10, sum = 0;
    for (int i = 1; i <= n; i++) {
        sum += i;
    }
    printf("Sum: %d\n", sum);
    return 0;
}

Calculates the sum of first N natural numbers using a for loop and demonstrates basic arithmetic operations.

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Factorial of a Number

#include <stdio.h>

int main() {
    int n = 5, fact = 1;

    for (int i = 1; i <= n; i++) {
        fact *= i;

    }

    printf("Factorial: %d\n", fact);

    return 0;

}

Calculates factorial of a number using iterative multiplication. Demonstrates loops and basic math operations.

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Check Even or Odd

#include <stdio.h>

int main() {
    int n = 7;

    if (n % 2 == 0)

        printf("%d is Even\n", n);

    else

        printf("%d is Odd\n", n);

    return 0;

}

Uses modulo operator to determine if a number is even or odd. Basic conditional logic demonstration.

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Reverse a Number

#include <stdio.h>

int main() {
    int n = 1234, rev = 0;

    while (n != 0) {
        rev = rev * 10 + n % 10;

        n /= 10;

    }

    printf("Reversed: %d\n", rev);

    return 0;

}

Reverses a number using modulo and division operations. Shows digit manipulation and while loop usage.

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Find Largest of Three Numbers

#include <stdio.h>

int main() {
    int a = 10, b = 20, c = 15;

    if (a >= b && a >= c)

        printf("Largest: %d\n", a);

    else if (b >= a && b >= c)

        printf("Largest: %d\n", b);

    else

        printf("Largest: %d\n", c);

    return 0;

}

Finds the largest number among three using nested if-else statements. Demonstrates comparison operations.

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Swap Two Numbers

#include <stdio.h>

int main() {
    int a = 5, b = 10, temp;

    temp = a;

    a = b;

    b = temp;

    printf("a = %d, b = %d\n", a, b);

    return 0;

}

Demonstrates swapping two numbers using a temporary variable. Basic variable manipulation example.

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Fibonacci Series

#include <stdio.h>

int main() {
    int n = 10, a = 0, b = 1, c;

    printf("%d %d ", a, b);

    for (int i = 2; i < n; i++) {
        c = a + b;

        printf("%d ", c);

        a = b;

        b = c;

    }

    return 0;

}

Generates Fibonacci sequence using iteration. Shows sequence generation and variable updates.

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Palindrome Check

#include <stdio.h>

int main() {
    int n = 121, orig = n, rev = 0;

    while (n != 0) {
        rev = rev * 10 + n % 10;

        n /= 10;

    }

    if (orig == rev)

        printf("Palindrome\n");

    else

        printf("Not Palindrome\n");

    return 0;

}

Checks if a number reads the same forwards and backwards. Uses digit extraction and reversal.

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Prime Number Check

#include <stdio.h>

int main() {
    int n = 29, isPrime = 1;

    for (int i = 2; i <= n / 2; i++) {
        if (n % i == 0) {
        isPrime = 0;

        break;

        }

    }

    if (isPrime)

        printf("%d is Prime\n", n);

    else

        printf("%d is Not Prime\n", n);

    return 0;

}

Determines if a number is prime by checking divisibility up to square root. Shows optimization in prime checking.

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Print Personal Information

#include <stdio.h>

int main() {
    printf("Name: Saurav\n");
    printf("Address: Nepal\n");
    printf("Age: 21\n");
    return 0;
}

Prints personal details like name, address, and age using printf statements.

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Structure of C Program

#include <stdio.h>

int main() {
    printf("This is a basic C program\n");
    return 0;
}

Demonstrates the basic structure of a C program.

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Syntax Error Example

#include <stdio.h>

int main() {
    int a = 10;
    printf("Value of a: %d\n", a);
    return 0;
}

Contains a syntax error for debugging practice.

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Logical Error Example

#include <stdio.h>

int main() {
    int l = 10, b = 5;
    int area = l + b;
    printf("Area = %d\n", area);
    return 0;
}

Program runs but gives incorrect output due to logical error.

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Runtime Error Example

#include <stdio.h>

int main() {
    int a = 10, b = 0;
    int c = a / b;
    printf("Result = %d\n", c);
    return 0;
}

Demonstrates runtime error caused by division by zero.

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Comments and Documentation Example

#include <stdio.h>

/*
    Program Name: Simple Addition
    Description: Adds two integers
    Author: Student
*/

int main() {
    int a = 5, b = 7;
    int sum = a + b;
    printf("Sum = %d\n", sum);
    return 0;
}

Demonstrates use of comments and documentation in C.

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Frequently Asked Questions about C

What is C?

C is a general-purpose, procedural programming language that provides low-level access to memory, efficient performance, and a foundation for system and application software development.

What are the primary use cases for C?

What are the strengths of C?

High performance and low overhead. Portable across platforms. Fine control over system resources. Large ecosystem and mature tooling. Foundation for many other programming languages

What are the limitations of C?

How can I practice C typing speed?

CodeSpeedTest offers 16+ real C code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.