Language: C

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

int main(){
  char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
  char s[1];
  int sp = 0;

  printf("%s", s);

  while(s[0] != c[sp]) sp++;

  sp++;

  printf("%s\n", c[sp]);

  return 0;
}


Compiler output:
main.c: In function 'main':
main.c:6:17: error: 'a' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                 ^
main.c:6:17: note: each undeclared identifier is reported only once for each function it appears in
main.c:6:19: error: 'b' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                   ^
main.c:6:21: error: initialization of 'char' from 'char *' makes integer from pointer without a cast [-Wint-conversion]
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                     ^
main.c:6:21: note: (near initialization for 'c[2]')
main.c:6:23: error: 'd' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                       ^
main.c:6:25: error: 'e' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                         ^
main.c:6:27: error: 'f' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                           ^
main.c:6:29: error: 'g' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                             ^
main.c:6:31: error: 'h' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                               ^
main.c:6:33: error: 'i' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                 ^
main.c:6:35: error: 'j' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                   ^
main.c:6:37: error: 'k' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                     ^
main.c:6:39: error: 'l' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                       ^
main.c:6:41: error: 'm' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                         ^
main.c:6:43: error: 'n' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                           ^
main.c:6:45: error: 'o' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                             ^
main.c:6:47: error: 'p' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                               ^
main.c:6:49: error: 'q' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                                 ^
main.c:6:51: error: 'r' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                                   ^
main.c:6:53: error: 's' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                                     ^
main.c:6:55: error: 't' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                                       ^
main.c:6:57: error: 'u' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                                         ^
main.c:6:59: error: 'w' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                                           ^
main.c:6:61: error: 'x' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                                             ^
main.c:6:63: error: 'y' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                                               ^
main.c:6:65: error: 'z' undeclared (first use in this function)
    6 |   char c[26] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,w,x,y,z};
      |                                                                 ^