Language: C

#include<stdio.h>

int main(){
	int i;
	int n;
	int old;
	int a = 0, 0, 0, 0, 0, 0, 0;
	
	while(n != 0){
		scanf("%d", &n);
			for(i = n + 1; i > 0; i--){
				scanf("%d", &old);
			    if(old < 10){
					a[0]++;
				}else if(old < 20){
				    a[1]++;
				}else if(old < 30){
				    a[2]++;
				}else if(old < 40){
				    a[3]++;
				}else if(old < 50){
				    a[4]++;
				}else if(old < 60){
					a[5]++;
				}else{
			        a[6]++;
		        }
			}
		printf("%d\n", a[0]);
		printf("%d\n", a[1]);
		printf("%d\n", a[2]);
		printf("%d\n", a[3]);
		printf("%d\n", a[4]);
		printf("%d\n", a[5]);
		printf("%d\n", a[6]);
	}
	
	return 0;

}

Compiler output:
main.c: In function 'main':
main.c:7:20: error: expected identifier or '(' before numeric constant
    7 |         int a = 0, 0, 0, 0, 0, 0, 0;
      |                    ^
main.c:14:42: error: subscripted value is neither array nor pointer nor vector
   14 |                                         a[0]++;
      |                                          ^
main.c:16:38: error: subscripted value is neither array nor pointer nor vector
   16 |                                     a[1]++;
      |                                      ^
main.c:18:38: error: subscripted value is neither array nor pointer nor vector
   18 |                                     a[2]++;
      |                                      ^
main.c:20:38: error: subscripted value is neither array nor pointer nor vector
   20 |                                     a[3]++;
      |                                      ^
main.c:22:38: error: subscripted value is neither array nor pointer nor vector
   22 |                                     a[4]++;
      |                                      ^
main.c:24:42: error: subscripted value is neither array nor pointer nor vector
   24 |                                         a[5]++;
      |                                          ^
main.c:26:34: error: subscripted value is neither array nor pointer nor vector
   26 |                                 a[6]++;
      |                                  ^
main.c:29:33: error: subscripted value is neither array nor pointer nor vector
   29 |                 printf("%d\n", a[0]);
      |                                 ^
main.c:30:33: error: subscripted value is neither array nor pointer nor vector
   30 |                 printf("%d\n", a[1]);
      |                                 ^
main.c:31:33: error: subscripted value is neither array nor pointer nor vector
   31 |                 printf("%d\n", a[2]);
      |                                 ^
main.c:32:33: error: subscripted value is neither array nor pointer nor vector
   32 |                 printf("%d\n", a[3]);
      |                                 ^
main.c:33:33: error: subscripted value is neither array nor pointer nor vector
   33 |                 printf("%d\n", a[4]);
      |                                 ^
main.c:34:33: error: subscripted value is neither array nor pointer nor vector
   34 |                 printf("%d\n", a[5]);
      |                                 ^
main.c:35:33: error: subscripted value is neither array nor pointer nor vector
   35 |                 printf("%d\n", a[6]);
      |                                 ^