How to Create a Calculator with C and Python

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C is a powerful programming language that provides low-level control and efficient performance. It is widely used for system programming, embedded systems, and developing applications where speed and memory management are crucial.

In this article, we will guide you through the steps to create a simple calculator using C, highlighting the differences between C and Python along the way.

Setting Up the Environment

To begin, you need a C compiler installed on your computer. There are various options available, such as GCC (GNU Compiler Collection), Visual Studio, or Codeblocks. Choose the one that suits your platform and install it. We would be using Codeblock, download it here.

To get started with this article, fork the repo and make sure to have a text editor.

Creating the Program

Open a text editor and create a new file. Save it with a “.c” extension, such as “calculator.c”. This file will contain the source code for your calculator.

Including the Required Libraries

In C, you need to include the necessary libraries at the beginning of your program. For this calculator, you only need the standard input/output library, so include the line:

#include <stdio.h>

Writing the Main Function

In C, the execution of a program begins from the main() function. Define the main() function as follows:

int main()
    // Code goes here
    return 0;

Declaring Variables

Declare the variables num1 and num2 to store the operands, operator to store the operator, and answer to store the result. Also, declare the terminate variable to control the continuation of the calculator loop:

int num1, num2;
char operator;
char terminate;
int answer;

Implementing the Calculator Loop

Use a do-while loop to continuously prompt the user for input and perform calculations until the user decides to exit. Inside the loop, you will take input from the user, perform the operation, and display the result.

If an invalid operator is entered, display an error message and continue the loop. The loop should terminate when the user enters ‘n’ or ‘N’:

do {
    // Code goes here
} while (terminate != 'n' && terminate != 'N');

Taking User Input

Inside the loop, prompt the user to enter the first number, operator, and second number. Use scanf() to read the input from the user. Remember to use getchar() after reading the first number and operator to clear the input buffer:

printf("Input the first number: ");
scanf("%d", &num1);

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

printf("Input the second number: ");
scanf("%d", &num2);

Performing the Calculation

Implement a switch statement to perform the appropriate operation based on the operator entered by the user. Calculate the answer and store it in the answer variable. If an invalid operator is entered, display an error message and use continue to skip the rest of the loop:

switch (operator) {
    case '+':
        answer = num1 + num2;
    case '-':
        answer = num1 - num2;
    case '*':
        answer = num1 * num2;
    case '/':
        answer = num1 / num2;
        printf("Invalid operator\n");

Displaying the Result

After calculating the answer, display it to the user using the printf() function:

printf("Answer: %d\n", answer);

Prompting for Continuation

Ask the user if they want to continue using the calculator. Prompt them to enter ‘y’ or ‘n’ and read their input using scanf(). Remember to use getchar() after reading the input to clear the input buffer:

printf("Do you want to continue? (y/n): ");

scanf(" %c", &terminate);


Finalizing the Program

Add the necessary closing braces to end the do-while loop and the main() function:

} while (terminate != 'n' && terminate != 'N');
return 0;

Compile and Run the Program

Click on run button at the top of your code blocks terminal to see the output if your code is without error, you will get an output like this.

Differences Between C and Python in Creating a Calculator

  • Syntax

C and Python have different syntax structures. C uses curly braces {} to define code blocks and requires explicit variable declarations, while Python uses indentation to define code blocks and has dynamic typing.

  • Data Types

C is a statically typed language, meaning you must explicitly declare variable types. Conversely, Python is dynamically typed, allowing variables to change their type during runtime.

  • Input/Output Handling

C uses functions like scanf() and printf() to handle input and output, requiring explicit format specifiers. Python provides simple built-in functions like input() and print() that handle input and output automatically.

  • Standard Libraries

C has a minimal standard library, requiring explicit inclusion of specific libraries for various operations. Python comes with a rich standard library that provides extensive functionalities, including mathematical operations, making it easier to create a calculator.

Creating a Calculator with Python

Creating a calculator with Python is relatively simpler due to its high-level nature and rich standard library. Here’s an example of a basic calculator program in Python:

while True:
    num1 = float(input("Input the first number: "))
    operator = input("Input the operator (-, +, *, /): ")
    num2 = float(input("Input the second number: "))

    if operator == '+':
        answer = num1 + num2
    elif operator == '-':
        answer = num1 - num2
    elif operator == '*':
        answer = num1 * num2
    elif operator == '/':
        answer = num1 / num2
        print("Invalid operator")

    print("Answer:", answer)

    terminate = input("Do you want to continue? (y/n): ")
    if terminate.lower() != 'y':
  1. The code starts with an infinite loop using while True. This means the program will keep running until it encounters a break statement.
  1. Inside the loop, the program prompts the user to input the first number using input(“Input the first number: “). The input is then converted to a floating-point number using float() and assigned to the variable num1.
  1. The program then prompts the user to input the operator they want to use (+, -, , /) using input(“Input the operator (-, +, , /): “). The input is stored in the variable operator.
  1. Next, the program prompts the user to input the second number using input(“Input the second number: “). Like the first number, the input is converted to a floating-point number and assigned to the variable num2.
  1. The program uses an if-elif-else statement to check the value of operator. The program performs the corresponding arithmetic operation depending on the operator entered and stores the result in the variable answer.
  1. If the operator entered is not one of the valid options (+, -, *, /), the program prints “Invalid operator” and uses the continue statement to skip the rest of the loop and start the next iteration.
  2. After calculating, the program prints the answer using print(“Answer:”, answer).
  1. The program prompts the user to decide whether to continue or not using input(“Do you want to continue? (y/n): “). The input is stored in the variable terminate.
  1. If the value of terminate converted to lowercase is not equal to ‘y’, the program breaks out of the infinite loop using break, thereby ending the program.

This code allows users to perform basic arithmetic operations by continuously entering numbers and operators. It provides the result and offers the option to continue or exit the calculator.

Frequently Asked Questions (FAQs)

What is C used for?

C is a versatile programming language used for various applications, including operating systems, embedded systems, device drivers, game development, high-performance computing, and more. Its efficiency, low-level control, and portability make it ideal for systems programming and developing performance-critical software.

Why choose C over Python for certain applications?

C is chosen over Python in scenarios where low-level control, efficient memory usage, and direct hardware interaction are critical. Applications that require real-time processing, extensive computational capabilities, or resource-constrained environments often benefit from using C. C is often preferred when code execution speed is a top priority, as C programs can be highly optimized for performance.

Is C harder to learn than Python?

The difficulty of learning a programming language depends on individual preferences and prior experience. C may have a steeper learning curve than Python due to its lower-level nature, explicit memory management, and complex syntax. However, once you grasp the fundamental concepts of C, it can provide a deeper understanding of computer architecture and programming principles. On the other hand, Python is known for its simplicity and readability, making it easier for beginners to understand and start coding quickly.

Can I create a GUI calculator using C?

Yes, you can create a GUI calculator using C. C provides libraries like GTK, Qt, and WinAPI that enable graphical user interface development. However, GUI programming in C requires more code and manual handling of UI elements than higher-level languages like Python, which have dedicated GUI frameworks like Tkinter and PyQt.

Are there any limitations or challenges when creating a calculator with C?

When creating a calculator or any program with C, you must manually handle user input validation and error checking. C does not provide built-in mechanisms for handling user input or exception handling. Memory management in C also requires manual allocation and deallocation, which can be error-prone if not done correctly.


C is a powerful language for creating efficient and low-level programs like calculators. Its performance, control over hardware, and portability make it a preferred choice for system-level programming.

However, Python’s simplicity, readability, and an extensive standard library make it a popular choice for rapid development and tasks that don’t require low-level control.

The choice between C and Python ultimately depends on the specific requirements and constraints of the project at hand.

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