Language: C

#include <stdio.h>

int main(void)
{
  char s[1200];
  int cnt[26] = {0};
  int i;

  gets(s);

  for(i = 0; i < 1200; i++){
    switch(s[i]){
    case 'a', 'A' : cnt[0]++;
    case 'b', 'B' : cnt[1]++;
    case 'c', 'C' : cnt[2]++;
    case 'd', 'D' : cnt[3]++;
    case 'e', 'E' : cnt[4]++;
    case 'f', 'F' : cnt[5]++;
    case 'g', 'G' : cnt[6]++;
    case 'h', 'H' : cnt[7]++;
    case 'i', 'I' : cnt[8]++;
    case 'j', 'J' : cnt[9]++;
    case 'k', 'K' : cnt[10]++;
    case 'l', 'L' : cnt[11]++;
    case 'm', 'M' : cnt[12]++;
    case 'n', 'N' : cnt[13]++;
    case 'o', 'O' : cnt[14]++;
    case 'p', 'P' : cnt[15]++;
    case 'q', 'Q' : cnt[16]++;
    case 'r', 'R' : cnt[17]++;
    case 's', 'S' : cnt[18]++;
    case 't', 'T' : cnt[19]++;
    case 'u', 'U' : cnt[20]++;
    case 'v', 'V' : cnt[21]++;
    case 'w', 'W' : cnt[22]++;
    case 'x', 'X' : cnt[23]++;
    case 'y', 'Y' : cnt[24]++;
    case 'z', 'Z' : cnt[25]++;
  }

  for(i = 0; i < 26; i++)
    printf("%c : %d\n", 'a' + i, cnt[i]);

  return 0;
}

Compiler output:
main.c: In function 'main':
main.c:9:3: error: implicit declaration of function 'gets'; did you mean 'fgets'? [-Wimplicit-function-declaration]
    9 |   gets(s);
      |   ^~~~
      |   fgets
main.c:13:13: error: expected ':' or '...' before ',' token
   13 |     case 'a', 'A' : cnt[0]++;
      |             ^
main.c:13:13: error: expected expression before ',' token
main.c:14:13: error: expected ':' or '...' before ',' token
   14 |     case 'b', 'B' : cnt[1]++;
      |             ^
main.c:14:13: error: expected expression before ',' token
main.c:15:13: error: expected ':' or '...' before ',' token
   15 |     case 'c', 'C' : cnt[2]++;
      |             ^
main.c:15:13: error: expected expression before ',' token
main.c:16:13: error: expected ':' or '...' before ',' token
   16 |     case 'd', 'D' : cnt[3]++;
      |             ^
main.c:16:13: error: expected expression before ',' token
main.c:17:13: error: expected ':' or '...' before ',' token
   17 |     case 'e', 'E' : cnt[4]++;
      |             ^
main.c:17:13: error: expected expression before ',' token
main.c:18:13: error: expected ':' or '...' before ',' token
   18 |     case 'f', 'F' : cnt[5]++;
      |             ^
main.c:18:13: error: expected expression before ',' token
main.c:19:13: error: expected ':' or '...' before ',' token
   19 |     case 'g', 'G' : cnt[6]++;
      |             ^
main.c:19:13: error: expected expression before ',' token
main.c:20:13: error: expected ':' or '...' before ',' token
   20 |     case 'h', 'H' : cnt[7]++;
      |             ^
main.c:20:13: error: expected expression before ',' token
main.c:21:13: error: expected ':' or '...' before ',' token
   21 |     case 'i', 'I' : cnt[8]++;
      |             ^
main.c:21:13: error: expected expression before ',' token
main.c:22:13: error: expected ':' or '...' before ',' token
   22 |     case 'j', 'J' : cnt[9]++;
      |             ^
main.c:22:13: error: expected expression before ',' token
main.c:23:13: error: expected ':' or '...' before ',' token
   23 |     case 'k', 'K' : cnt[10]++;
      |             ^
main.c:23:13: error: expected expression before ',' token
main.c:24:13: error: expected ':' or '...' before ',' token
   24 |     case 'l', 'L' : cnt[11]++;
      |             ^
main.c:24:13: error: expected expression before ',' token
main.c:25:13: error: expected ':' or '...' before ',' token
   25 |     case 'm', 'M' : cnt[12]++;
      |             ^
main.c:25:13: error: expected expression before ',' token
main.c:26:13: error: expected ':' or '...' before ',' token
   26 |     case 'n', 'N' : cnt[13]++;
      |             ^
main.c:26:13: error: expected expression before ',' token
main.c:27:13: error: expected ':' or '...' before ',' token
   27 |     case 'o', 'O' : cnt[14]++;
      |             ^
main.c:27:13: error: expected expression before ',' token
main.c:28:13: error: expected ':' or '...' before ',' token
   28 |     case 'p', 'P' : cnt[15]++;
      |             ^
main.c:28:13: error: expected expression before ',' token
main.c:29:13: error: expected ':' or '...' before ',' token
   29 |     case 'q', 'Q' : cnt[16]++;
      |             ^
main.c:29:13: error: expected expression before ',' token
main.c:30:13: error: expected ':' or '...' before ',' token
   30 |     case 'r', 'R' : cnt[17]++;
      |             ^
main.c:30:13: error: expected expression before ',' token
main.c:31:13: error: expected ':' or '...' before ',' token
   31 |     case 's', 'S' : cnt[18]++;
      |             ^
main.c:31:13: error: expected expression before ',' token
main.c:32:13: error: expected ':' or '...' before ',' token
   32 |     case 't', 'T' : cnt[19]++;
      |             ^
main.c:32:13: error: expected expression before ',' token
main.c:33:13: error: expected ':' or '...' before ',' token
   33 |     case 'u', 'U' : cnt[20]++;
      |             ^
main.c:33:13: error: expected expression before ',' token
main.c:34:13: error: expected ':' or '...' before ',' token
   34 |     case 'v', 'V' : cnt[21]++;
      |             ^
main.c:34:13: error: expected expression before ',' token
main.c:35:13: error: expected ':' or '...' before ',' token
   35 |     case 'w', 'W' : cnt[22]++;
      |             ^
main.c:35:13: error: expected expression before ',' token
main.c:36:13: error: expected ':' or '...' before ',' token
   36 |     case 'x', 'X' : cnt[23]++;
      |             ^
main.c:36:13: error: expected expression before ',' token
main.c:37:13: error: expected ':' or '...' before ',' token
   37 |     case 'y', 'Y' : cnt[24]++;
      |             ^
main.c:37:13: error: expected expression before ',' token
main.c:38:13: error: expected ':' or '...' before ',' token
   38 |     case 'z', 'Z' : cnt[25]++;
      |             ^
main.c:38:13: error: expected expression before ',' token
main.c:45:1: error: expected declaration or statement at end of input
   45 | }
      | ^