C Program To Make Simple Calculatorc Program That Gets Two Strings From Input And Stores Them In Variables Such As Str1 And Str2

This article guides you through creating a simple calculator program in C. You will learn how to accept user input for two numbers and an arithmetic operator, then perform the corresponding calculation and display the result.

Problem Statement

Many everyday tasks require basic arithmetic operations, such as addition, subtraction, multiplication, and division. Building a simple command-line calculator addresses the need for a quick, accessible tool to perform these calculations without requiring a graphical interface.

Example

The calculator will prompt the user for two numbers and an operator. For instance, if a user enters 10, +, and 5, the output will be 15.0.

Background & Knowledge Prerequisites

To understand and implement this C program, you should have a basic understanding of:

• C data types: int for integers, float or double for decimal numbers.
• Input/Output functions: printf() for displaying output and scanf() for reading input.
• Arithmetic operators: +, -, *, /.
• Conditional statements: if-else or switch statements for decision-making.

Use Cases or Case Studies

A simple calculator program can be incredibly useful in various scenarios:

• Learning C Programming: It serves as an excellent beginner project to practice fundamental C concepts like I/O, variables, and control flow.
• Quick Command-Line Calculations: Developers or users working in a terminal environment can quickly perform calculations without switching applications.
• Embedding in Larger Systems: The core logic can be a component within a larger application that requires basic computational capabilities.
• Educational Tools: Teachers can use it to demonstrate basic programming principles or mathematics.
• Basic Scripting: For simple batch scripts or automated tasks where quick calculations are needed.

Solution Approaches

We will implement a straightforward approach using a switch statement to handle different arithmetic operations.

Simple Calculator using switch statement

This approach takes two numbers and an operator from the user, then uses a switch statement to execute the appropriate arithmetic operation.

// Simple C Calculator
#include <stdio.h>

int main() {
    // Step 1: Declare variables to store numbers, operator, and result
    char operator_char;
    double num1, num2, result;

    // Step 2: Prompt user for the first number
    printf("Enter first number: ");
    scanf("%lf", &num1);

    // Step 3: Prompt user for the operator
    printf("Enter an operator (+, -, *, /): ");
    scanf(" %c", &operator_char); // Note the space before %c to consume newline

    // Step 4: Prompt user for the second number
    printf("Enter second number: ");
    scanf("%lf", &num2);

    // Step 5: Use a switch statement to perform the calculation based on the operator
    switch (operator_char) {
        case '+':
            result = num1 + num2;
            printf("Result: %.2lf + %.2lf = %.2lf\\n", num1, num2, result);
            break;
        case '-':
            result = num1 - num2;
            printf("Result: %.2lf - %.2lf = %.2lf\\n", num1, num2, result);
            break;
        case '*':
            result = num1 * num2;
            printf("Result: %.2lf * %.2lf = %.2lf\\n", num1, num2, result);
            break;
        case '/':
            // Handle division by zero
            if (num2 == 0) {
                printf("Error: Division by zero is not allowed.\\n");
            } else {
                result = num1 / num2;
                printf("Result: %.2lf / %.2lf = %.2lf\\n", num1, num2, result);
            }
            break;
        default:
            printf("Error: Invalid operator entered.\\n");
            break;
    }

    return 0;
}

Run

Sample Output

Enter first number: 10
Enter an operator (+, -, *, /): *
Enter second number: 4
Result: 10.00 * 4.00 = 40.00

Enter first number: 7
Enter an operator (+, -, *, /): /
Enter second number: 0
Error: Division by zero is not allowed.

Stepwise Explanation

1. Variable Declaration: We declare operator_char of type char to store the arithmetic operator, and num1, num2, result of type double to handle floating-point numbers for more precise calculations.
2. Input for First Number: The program prompts the user to enter the first number using printf() and reads it into num1 using scanf("%lf", &num1). The %lf format specifier is used for reading double values.
3. Input for Operator: The user is then asked to enter an operator. scanf(" %c", &operator_char) reads the character. The space before %c is crucial; it tells scanf to consume any leftover whitespace characters (like the newline character from the previous scanf) before reading the actual character.
4. Input for Second Number: Similarly, the second number is prompted and read into num2.
5. Conditional Calculation (Switch):

• A switch statement evaluates the operator_char.
• For each case (+, -, *, /), the corresponding arithmetic operation is performed, and the result is stored in the result variable.
• The printf() function displays the calculation and its result, formatted to two decimal places (.2lf).
• Division by Zero Handling: Specifically for the division case (/), an if statement checks if num2 is zero. If it is, an error message is printed to prevent a runtime error. Otherwise, the division proceeds.
• The break statement exits the switch block after a matching case is found.
• The default case catches any invalid operator input, printing an error message.

1. Return 0: The main function returns 0 to indicate successful execution.

Conclusion

Creating a simple calculator in C demonstrates fundamental programming concepts, including user input/output, variable handling, arithmetic operations, and conditional logic. This basic structure can be expanded upon for more complex calculations or features.

Summary

• A C program can implement a basic calculator by taking two numbers and an operator as input.
• The scanf() and printf() functions are essential for handling user input and displaying results.
• The switch statement provides a clean way to manage different arithmetic operations based on the user's operator choice.
• Error handling, such as preventing division by zero, is crucial for robust programs.
• This project is excellent for practicing core C programming skills and understanding control flow.