C Programming Practice: Hello World, Calculator, and Swap Numbers

This tutorial provides beginner-friendly practice programs in C programming, including a "Hello World" program, a simple calculator, and swapping two numbers. These examples help beginners understand program structure, input/output, operators, and variables.

1. Hello World Program

Description

The first program in C that demonstrates basic syntax and output using printf().

Code Example


#include <stdio.h>

int main() {
printf("Hello, World!\n");
return 0;
}

Output


Hello, World!

2. Simple Calculator

Description

A program to perform basic arithmetic operations (+, -, *, /) using user input and switch statement.

Code Example


#include <stdio.h>

int main() {
char operator;
float num1, num2, result;

printf("Enter operator (+, -, *, /): ");
scanf(" %c", &operator);

printf("Enter two numbers: ");
scanf("%f %f", &num1, &num2);

switch(operator) {
case '+':
result = num1 + num2;
break;
case '-':
result = num1 - num2;
break;
case '*':
result = num1 * num2;
break;
case '/':
if(num2 != 0)
result = num1 / num2;
else {
printf("Error! Division by zero.\n");
return 1;
}
break;
default:
printf("Invalid operator\n");
return 1;
}

printf("Result: %.2f\n", result);
return 0;
}

Sample Output


Enter operator (+, -, *, /): +
Enter two numbers: 10 5
Result: 15.00

3. Swap Two Numbers

Description

A program to swap the values of two variables using:

  1. A temporary variable
  2. Without temporary variable

Method 1: Using Temporary Variable


#include <stdio.h>

int main() {
int a, b, temp;

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

temp = a;
a = b;
b = temp;

printf("After swapping: a = %d, b = %d\n", a, b);
return 0;
}

Method 2: Without Temporary Variable


#include <stdio.h>

int main() {
int a, b;

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

a = a + b;
b = a - b;
a = a - b;

printf("After swapping: a = %d, b = %d\n", a, b);
return 0;
}

Sample Output


Enter two numbers: 10 20
After swapping: a = 20, b = 10

Key Points to Remember

  1. Always include <stdio.h> for I/O functions
  2. Use return 0; to indicate successful program execution
  3. Take care of operator precedence in calculations
  4. Swapping can be done with or without a temporary variable