I am trying to make a calculator for resistor. So the input is a value in Ohms and the output will be the color band of the resistor.

But I've been stuck in this for a while, I'm not sure what is happening. No matter what, the code always go to the default situation.

char a, b, c; 
int tolerancia,valor;
  
printf("enter resistance value:  ");
scanf("%i", &valor);

c = valor % 10; // th
b = (valor % 100) / 10; // second digit
a = valor / 100; //  first digit

switch (a)                    //colour band for first digit//
{
    case '0':
    printf("black   ");
    break;
    
    case '1':
    printf("brown   ");
    break;
    
    case '2':
    printf("red   ");
    break;
    
    case '3':
    printf("orange   ");
    break;
    
    case '4':
    printf("yellow   ");
    break;
    
    case '5':
    printf("green   ");
    break;
    
    case '6':
    printf("blue   ");
    break;
    
    case '7':
    printf("violet   ");
    break;
    
    case '8':
    printf("grey   ");
    break;
    
    case '9':
    printf("white   ");
    break;
    
    default:
    printf("unknown value   ");
}

The switch case goes for 3 times (first digit, second digit and tolerance) and in every situation the output is "unknown value"

CodePudding user response：

You're reading an int, but your switch is comparing the first digit of that int to various characters. Now, char is a numeric type, so this (kind of) works, but the value of '0' does not equal 0 and so on for all digit characters.

Thus you go straight to the default case.

More correctly:

switch (a) {
    case 0:
    printf("black   ");
    break;

    // etc.
}

You could also simply have an array of strings and use the digit to index it. Making sure of course to validate that a is a valid index.

char *colors[] = { 
    "black", "brown", "red", "orange", "yellow", 
    "green", "blue", "violet", "grey", "white" 
};

if (a >= 0 && a <= 9) {
    printf("%s   ", colors[a]);
}
else {
    printf("unknown value   ");
}