C Programming: Temperature Converter – Celsius, Fahrenheit, and Kelvin

Temperature conversion is a fundamental programming exercise that teaches essential C programming concepts. In this tutorial, we’ll build a comprehensive temperature converter that handles Celsius, Fahrenheit, and Kelvin conversions with proper input validation and user-friendly interface.

Learning Objectives

• Understanding mathematical operations in C
• Working with floating-point arithmetic
• Implementing menu-driven programs
• Input validation and error handling
• Creating reusable functions

Basic Temperature Converter

#include <stdio.h>

int main() {
    float celsius, fahrenheit, kelvin;
    int choice;
    
    printf("==========================================\n");
    printf("       TEMPERATURE CONVERTER PROGRAM     \n");
    printf("==========================================\n\n");
    
    printf("Select conversion type:\n");
    printf("1. Celsius to Fahrenheit\n");
    printf("2. Fahrenheit to Celsius\n");
    printf("3. Celsius to Kelvin\n");
    printf("4. Kelvin to Celsius\n");
    printf("5. Fahrenheit to Kelvin\n");
    printf("6. Kelvin to Fahrenheit\n");
    printf("Enter your choice (1-6): ");
    scanf("%d", &choice);
    
    switch(choice) {
        case 1:
            printf("Enter temperature in Celsius: ");
            scanf("%f", &celsius);
            fahrenheit = (celsius * 9.0/5.0) + 32;
            printf("%.2f°C = %.2f°F\n", celsius, fahrenheit);
            break;
            
        case 2:
            printf("Enter temperature in Fahrenheit: ");
            scanf("%f", &fahrenheit);
            celsius = (fahrenheit - 32) * 5.0/9.0;
            printf("%.2f°F = %.2f°C\n", fahrenheit, celsius);
            break;
            
        case 3:
            printf("Enter temperature in Celsius: ");
            scanf("%f", &celsius);
            kelvin = celsius + 273.15;
            printf("%.2f°C = %.2fK\n", celsius, kelvin);
            break;
            
        case 4:
            printf("Enter temperature in Kelvin: ");
            scanf("%f", &kelvin);
            if (kelvin < 0) {
                printf("Error: Temperature cannot be below absolute zero!\n");
            } else {
                celsius = kelvin - 273.15;
                printf("%.2fK = %.2f°C\n", kelvin, celsius);
            }
            break;
            
        case 5:
            printf("Enter temperature in Fahrenheit: ");
            scanf("%f", &fahrenheit);
            kelvin = (fahrenheit - 32) * 5.0/9.0 + 273.15;
            printf("%.2f°F = %.2fK\n", fahrenheit, kelvin);
            break;
            
        case 6:
            printf("Enter temperature in Kelvin: ");
            scanf("%f", &kelvin);
            if (kelvin < 0) {
                printf("Error: Temperature cannot be below absolute zero!\n");
            } else {
                fahrenheit = (kelvin - 273.15) * 9.0/5.0 + 32;
                printf("%.2fK = %.2f°F\n", kelvin, fahrenheit);
            }
            break;
            
        default:
            printf("Invalid choice! Please run the program again.\n");
            break;
    }
    
    return 0;
}

Compilation and Execution

# Compile the program
gcc temperature_converter.c -o temp_converter

# Run the program
./temp_converter

Practice Exercises

1. Add Rankine temperature scale conversion
2. Create a batch conversion feature for multiple temperatures
3. Add historical temperature data comparison
4. Implement temperature range validation for different scales
5. Create a GUI version using graphics libraries

Next Steps

This temperature converter demonstrates fundamental C programming concepts and serves as a building block for more complex applications. In our next tutorial, we’ll explore creating a grade calculator with GPA computation and statistical analysis features.