Programa en C para hacer una calculadora simple

Podemos hacer una calculadora simple usando el lenguaje C mediante dos enfoques usando el cambio de mayúsculas y minúsculas y la instrucción if-else .

Aporte: 

7+8
8-9
8*7
8/3

Producción:

Enter an operator (+, -, *, /), if want to exit press x: +
Enter two first and second operand: 7 8
7.0 + 8.0 = 15.0
Enter an operator (+, -, *, /), if want to exit press x: -
Enter two first and second operand: 8 9
8.0 - 9.0 = -1.0
Enter an operator (+, -, *, /), if want to exit press x: *
Enter two first and second operand: 8 7
8.0 * 7.0 = 56.0
Enter an operator (+, -, *, /), if want to exit press x: /
Enter two first and second operand: 8 3
8.0 / 3.0 = 2.7
Enter an operator (+, -, *, /), if want to exit press x: x

Uso de la caja del interruptor:

Acercarse:

1. Haremos todos los siguientes pasos dentro de un bucle interminable para que el programa de calculadora siga funcionando.
2. Tome la entrada del operador y luego los operandos.
3. Verifique si el usuario desea salir del programa, si es así, luego ciérrelo, para esto, podemos usar un carácter especial y decirle al usuario al respecto como aquí usamos «x». 
4. Usar operadores de verificación de casos de cambio y hacer operaciones en consecuencia.

// C Program to Make a Simple Calculator
// Using switch case
#include <stdio.h>
#include <stdlib.h>
 
int main()
{
    char ch;
    double a, b;
    while (1) {
        printf("Enter an operator (+, -, *, /), if want to exit press x: ");
        scanf(" %c", &ch);
        // to exit
        if (ch == 'x')
            exit(0);
        printf("Enter two first and second operand: ");
        scanf("%lf %lf",&a,&b);
        // Using switch case we will differentiate
        // operations based on different operator
        switch (ch) {
        // For Addition
        case '+':
            printf("%.1lf + %.1lf = %.1lf\n", a, b, a + b);
            break;
        // For Subtraction
        case '-':
            printf("%.1lf - %.1lf = %.1lf\n", a, b, a - b);
            break;
        // For Multiplication
        case '*':
            printf("%.1lf * %.1lf = %.1lf\n", a, b, a * b);
            break;
        // For Division
        case '/':
            printf("%.1lf / %.1lf = %.1lf\n", a, b, a / b);
            break;
        // If operator doesn't match any case constant
        default:
            printf("Error! please write a valid operator\n");
        }
    }
}

Producción:

Enter an operator (+, -, *, /), if want to exit press x: +
Enter two first and second operand: 7 8
7.0 + 8.0 = 15.0
Enter an operator (+, -, *, /), if want to exit press x: -
Enter two first and second operand: 8 9
8.0 - 9.0 = -1.0
Enter an operator (+, -, *, /), if want to exit press x: *
Enter two first and second operand: 8 7
8.0 * 7.0 = 56.0
Enter an operator (+, -, *, /), if want to exit press x: /
Enter two first and second operand: 8 3
8.0 / 3.0 = 2.7
Enter an operator (+, -, *, /), if want to exit press x: x

Usando If-Else 

Acercarse:

1. Haremos todos los siguientes pasos dentro de un bucle interminable para que el programa de calculadora siga funcionando.
2. Tome la entrada del operador y luego los operandos.
3. Verifique si el usuario desea salir del programa, si es así, luego ciérrelo, para esto, podemos usar un carácter especial y decirle al usuario, como aquí usamos «x».
4. Usando sentencias if-else comprobaremos los operadores y haremos las operaciones correspondientes.

Ejemplo:

// C Program to Make a Simple Calculator
// Using if else statement
#include <stdio.h>
#include <stdlib.h>
 
int main()
{
    char ch;
    double a, b;
    while (1) {
        printf("Enter an operator (+, -, *, /), if want to exit press x: ");
        scanf(" %c", &ch);
        // to exit
        if (ch == 'x')
            exit(0);
        printf("Enter two first and second operand: ");
        scanf("%lf %lf", &a, &b);
        // Using if else we will differentiate operations
        // based on different operator
        if (ch == '+') {
            // For Addition
            printf("%.1lf + %.1lf = %.1lf\n", a, b, a + b);
        }
        else if (ch == '-') {
            // For Subtraction
            printf("%.1lf - %.1lf = %.1lf\n", a, b, a - b);
        }
        else if (ch == '*') {
            // For Multiplication
            printf("%.1lf * %.1lf = %.1lf\n", a, b, a * b);
        }
        else if (ch == '/') {
            // For Division
            printf("%.1lf / %.1lf = %.1lf\n", a, b, a / b);
        }
        else {
            // If operator doesn't match any case constant
            printf("Error! please write a valid operator\n");
        }
    }
}

Producción:

Enter an operator (+, -, *, /), if want to exit press x: +
Enter two first and second operand: 7 8
7.0 + 8.0 = 15.0
Enter an operator (+, -, *, /), if want to exit press x: -
Enter two first and second operand: 8 9
8.0 - 9.0 = -1.0
Enter an operator (+, -, *, /), if want to exit press x: *
Enter two first and second operand: 8 7
8.0 * 7.0 = 56.0
Enter an operator (+, -, *, /), if want to exit press x: /
Enter two first and second operand: 8 3
8.0 / 3.0 = 2.7
Enter an operator (+, -, *, /), if want to exit press x: x