c - 如何让 C 程序回复一封信并吐出其他内容？

Question

我似乎无法编译这个程序。

我不断收到错误:

'Ammonia' undeclared 'Carbon_Monoxide' undeclared

等等。我是否使用了正确的开关功能？

/*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

它与您的 switch 语句无关，但您可能不得不对这四行的含义感到困惑:

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

您没有在任何地方使用如此定义的变量，并且 undefined symbol “Ammonia”、“Carbon_Monoxide”等 - 这是您看到的错误的原因。