Language: C

#include <stdio.h>
#include <string.h> //strcmp、strncmp関数を使うために必要
 
int main(void){
  	char =a;
	scanf("%s",&a);
  
  switch(a){
    case a:printf("a");
          break;
      case b:printf("a");
          break;
      case c:printf("a");
          break;
      case d:printf("a");
          break;
      case e:printf("a");
          break;
      case f:printf("a");
          break;
      case g:printf("a");
          break;
      case h:printf("a");
          break;
      case i:printf("a");
          break;
      case j:printf("a");
          break;
      case k:printf("a");
          break;
      case l:printf("a");
          break;
      case m:printf("a");
          break;
      case n:printf("a");
          break;
      case o:printf("a");
          break;
      case p:printf("a");
          break;
      case q:printf("a");
          break;
      case r:printf("a");
          break;
      case s:printf("a");
          break;
      case t:printf("a");
          break;
      case u:printf("a");
          break;
      case v:printf("a");
          break;
      case w:printf("a");
          break;
      case x:printf("a");
          break;
      case y:printf("a");
          break;
      case z:printf("a");
          break;
     default :printf("A");
      			break;

  }

		return 0;
}

Compiler output:
main.c: In function 'main':
main.c:5:14: error: expected identifier or '(' before '=' token
    5 |         char =a;
      |              ^
main.c:6:21: error: 'a' undeclared (first use in this function)
    6 |         scanf("%s",&a);
      |                     ^
main.c:6:21: note: each undeclared identifier is reported only once for each function it appears in
main.c:11:12: error: 'b' undeclared (first use in this function)
   11 |       case b:printf("a");
      |            ^
main.c:13:12: error: 'c' undeclared (first use in this function)
   13 |       case c:printf("a");
      |            ^
main.c:15:12: error: 'd' undeclared (first use in this function)
   15 |       case d:printf("a");
      |            ^
main.c:17:12: error: 'e' undeclared (first use in this function)
   17 |       case e:printf("a");
      |            ^
main.c:19:12: error: 'f' undeclared (first use in this function)
   19 |       case f:printf("a");
      |            ^
main.c:21:12: error: 'g' undeclared (first use in this function)
   21 |       case g:printf("a");
      |            ^
main.c:23:12: error: 'h' undeclared (first use in this function)
   23 |       case h:printf("a");
      |            ^
main.c:25:12: error: 'i' undeclared (first use in this function)
   25 |       case i:printf("a");
      |            ^
main.c:27:12: error: 'j' undeclared (first use in this function)
   27 |       case j:printf("a");
      |            ^
main.c:29:12: error: 'k' undeclared (first use in this function)
   29 |       case k:printf("a");
      |            ^
main.c:31:12: error: 'l' undeclared (first use in this function)
   31 |       case l:printf("a");
      |            ^
main.c:33:12: error: 'm' undeclared (first use in this function)
   33 |       case m:printf("a");
      |            ^
main.c:35:12: error: 'n' undeclared (first use in this function)
   35 |       case n:printf("a");
      |            ^
main.c:37:12: error: 'o' undeclared (first use in this function)
   37 |       case o:printf("a");
      |            ^
main.c:39:12: error: 'p' undeclared (first use in this function)
   39 |       case p:printf("a");
      |            ^
main.c:41:12: error: 'q' undeclared (first use in this function)
   41 |       case q:printf("a");
      |            ^
main.c:43:12: error: 'r' undeclared (first use in this function)
   43 |       case r:printf("a");
      |            ^
main.c:45:12: error: 's' undeclared (first use in this function)
   45 |       case s:printf("a");
      |            ^
main.c:47:12: error: 't' undeclared (first use in this function)
   47 |       case t:printf("a");
      |            ^
main.c:49:12: error: 'u' undeclared (first use in this function)
   49 |       case u:printf("a");
      |            ^
main.c:51:12: error: 'v' undeclared (first use in this function)
   51 |       case v:printf("a");
      |            ^
main.c:53:12: error: 'w' undeclared (first use in this function)
   53 |       case w:printf("a");
      |            ^
main.c:55:12: error: 'x' undeclared (first use in this function)
   55 |       case x:printf("a");
      |            ^
main.c:57:12: error: 'y' undeclared (first use in this function)
   57 |       case y:printf("a");
      |            ^
main.c:59:12: error: 'z' undeclared (first use in this function)
   59 |       case z:printf("a");
      |            ^