Switch in C programming [duplicate]

Answer 1

The grammar for a switch statement in C is the following:

selection-statement:
switch ( expression ) statement
  labeled-statement:
  case constant-expression : statement
  default : statement

Therefore, you can only use constant expressions as "case value". Constant expression is not the same as constant variable. In other words - sorry, but you cannot do that.

Answer 2

case statements need constants. You could accomplish something similar to what you're doing with a macro.

#define TEN 10
#include<stdio.h>
int main()
{
int const  x = TEN;
int y = 20;
switch(y)
{
    case TEN:      //error: case label does not reduce to an integer constant
    printf("value of x: %d\n",x);   
    break;
}
}

Answer 3

you can use the preprocessor as a workaround:

#define X 10
// ...
case X:

Answer 4

In this case , you have to use a if statement becasue C's switch() does not take an expression. It takes a constant.

Answer 5

You might know that x is a constant but the compiler cannot guarantee it: it is still possible to modify x in C. One way is by taking its address (via a pointer) and dereferencing it.

In C you can only switch on literal integral types; more formally, a constant expression.