如何让C程序回复一封信并吐出其他东西？

Question

I can't seem to get this program to compile.

I keep getting the error:

'Ammonia' undeclared 'Carbon_Monoxide' undeclared

and so on. Am I using the right function with switch?

/*This program will report the content of a compressed-gas cylinder based on the first letter of the cylinder's color.*/


#include <stdio.h>
int main (void)
{ 
     int x; 
     char o, b, y, g;
     int pause;

     o = Ammonia;
     b = Carbon_Monoxide;
     y = Hydrogen;
     g = Oxygen;

     printf(" Enter a character representing the observed color of the cylinder \n" );
     scanf("%d", &x);
     switch (x)
     {

        case 'o': printf("The content is Ammonia\n");
        case 'b': printf("The content is Carbon Monoxide\n");
        case 'y': printf("The content is Hydrogen\n");
        case 'g': printf("The content is Oxygen\n");
        default: printf("Character out of range \n");
     }

     printf("After Switch \n");
     printf("Enter new character to continue \n");
     scanf("%d", &pause);

     return 0;
}

Answer 1

It has nothing to do with your switch statement, but you will probably have to puzzle over the meaning of these four lines:

 o = Ammonia;
 b = Carbon_Monoxide;
 y = Hydrogen;
 g = Oxygen;

You don't use the variables thus defined anywhere, and the symbols "Ammonia", "Carbon_Monoxide" and so on are not defined - this is the cause of the error you are seeing.

Answer 2

Since this is homework, I don't want to give you the answer straight, but look at what you're doing with those chars (o, b, y, g) and ask yourself if it makes sense.

Also, on the switch statement, I'm pretty sure you need a break; after each case, else it will print each case's statement

Answer 3

try:

#include <stdio.h>

int main (void)

{

    char x; 

    int pause;


    printf(" Enter a character representing the observed color of the cylinder \n" );
    scanf("%c", &x);


    while(x){
        switch (x)

        {

        case 'o': printf("The content is Ammonia\n"); break;
        case 'b': printf("The content is Carbon Monoxide\n"); break;
        case 'y': printf("The content is Hydrogen\n"); break;
        case 'g': printf("The content is Oxygen\n"); break;
        default: printf("Character out of range \n");

        }

        printf("After Switch \n");
        printf("Enter new character to continue \n");
        scanf(" %c", &x);

        if(x == 'q'){
            break;
        }
    }
    return 0;

}