$ gcc -o hw02test hw02.c hw02test.c
hw02test.c: In function ‘main’:
hw02test.c:5:2: warning: implicit declaration of function ‘print_integer’ [-Wimplicit-function-declaration]
  print_integer(1, 10, "");
--
TRANSLATION:   You are missing a header file or forward declaration.
GCC doesn't know what that function returns or what it is supposed to take.



$ diff <(./hw02test) hw02test.txt
1d0
< 1
\ No newline at end of file
--
TRANSLATION:  File has a newline (\n) at the end, but program didn't output a newline the end.
SOLUTION:  Add fputc('\n', stdout) or printf("\n") to end of your main();


$ gcc -o hw02test hw02.c hw02test.c
hw02.c: In function ‘print_integer’:
hw02.c:10:2: warning: passing argument 1 of ‘fputc’ makes integer from pointer without a cast [enabled by default]
  fputc("1", stdout);
  ^
In file included from hw02.c:2:0:
/usr/include/stdio.h:573:12: note: expected ‘int’ but argument is of type ‘char *’
 extern int fputc (int __c, FILE *__stream);
            ^
--
TRANSLATION:  Got a string literal (e.g., "1") where we expected a char constant ('1').
              Remember that to the compiler, a char constant is the same as an int constant.
SOLUTION:  Check your quotes.  "▒" is for a string literal.  '▒' is for a char constant.