Main.c: In function ‘main’:
Main.c:3:2: warning: implicit declaration of function ‘printHead’ [-Wimplicit-function-declaration]
    3 |  printHead();
      |  ^~~~~~~~~
Main.c:6:4: warning: implicit declaration of function ‘printf’ [-Wimplicit-function-declaration]
    6 |    printf("%-4d", i * j);
      |    ^~~~~~
Main.c:6:4: warning: incompatible implicit declaration of built-in function ‘printf’
Main.c:1:1: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
  +++ |+#include <stdio.h>
    1 | int main(void)
Main.c:8:3: warning: incompatible implicit declaration of built-in function ‘printf’
    8 |   printf("
");
      |   ^~~~~~
Main.c:8:3: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
Main.c:14:16: warning: incompatible implicit declaration of built-in function ‘printf’
   14 |    if (i >= j) printf("%-4d", i * j);
      |                ^~~~~~
Main.c:14:16: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
Main.c:16:3: warning: incompatible implicit declaration of built-in function ‘printf’
   16 |   printf("
");
      |   ^~~~~~
Main.c:16:3: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
Main.c:22:13: warning: incompatible implicit declaration of built-in function ‘printf’
   22 |    i <= j ? printf("%-4d", i * j) : printf("%-4c", ' ');
      |             ^~~~~~
Main.c:22:13: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
Main.c:24:3: warning: incompatible implicit declaration of built-in function ‘printf’
   24 |   printf("
");
      |   ^~~~~~
Main.c:24:3: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
/usr/bin/ld: /tmp/cceaTMin.o: in function `main':
Main.c:(.text.startup+0x1a): undefined reference to `printHead'
/usr/bin/ld: Main.c:(.text.startup+0x67): undefined reference to `printHead'
/usr/bin/ld: Main.c:(.text.startup+0xc9): undefined reference to `printHead'
collect2: error: ld returned 1 exit status