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

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

printf("Enter an operator (+, -, *, /): ");
scanf(" %c", &operator);  // Notice the space before %c to consume any newline character

printf("Enter second number: ");
scanf("%lf", &num2);

// Perform calculation based on operator
switch (operator) {
    case '+':
        result = num1 + num2;
        printf("%.2lf + %.2lf = %.2lf\n", num1, num2, result);
        break;
    case '-':
        result = num1 - num2;
        printf("%.2lf - %.2lf = %.2lf\n", num1, num2, result);
        break;
    case '*':
        result = num1 * num2;
        printf("%.2lf * %.2lf = %.2lf\n", num1, num2, result);
        break;
    case '/':
        // Check for division by zero
        if (num2 != 0) {
            result = num1 / num2;
            printf("%.2lf / %.2lf = %.2lf\n", num1, num2, result);
        } else {
            printf("Error: Division by zero is not allowed.\n");
        }
        break;
    default:
        printf("Error: Invalid operator.\n");
        break;
}

return 0;

}

Explanation:-

Headers and Main Function: The code begins by including the standard input-output library (<stdio.h>) and defining the main function.

Variables Declaration: Four variables are declared:

• operator: to store the arithmetic operator entered by the user.
• num1 and num2: to store the two numbers on which the operation will be performed.
• result: to store the result of the operation.

User Input:

• The program prompts the user to enter the first number, the operator, and the second number. The scanf function is used to read these inputs.

Switch Case Statement: This statement evaluates the operator variable:

• For each case (+, -, *, /), it performs the corresponding arithmetic operation and prints the result.
• If the operator is /, it checks if the second number is zero to prevent division by zero. If it is zero, an error message is displayed.

Default Case: If the user enters an invalid operator, the program outputs an error message.

Example:

Suppose a user runs the program and enters the following:

Enter first number: 10
Enter an operator (+, -, *, /): +
Enter second number: 5

10.00 + 5.00 = 15.00