Why is this code not working? it can print out what I had in the file, but in the do while loop it fail, the value of a I have is $0.$ then in gdb When I go to next line it just become $-1,$ and end.

char upper $($ char ch$)$

$\{$

; ;

return $($char$)($ch $-(\text{'}\{$:$a^{\text{'}}-{?}^{\text{'}}{A}^{\text{'}})$;

int main$($int argc, char$*$ argv$[])\{$

int $c$;

char $*$key $=$argv$[2]$;

int key$\_$length $=$ strlen key