I have already defined a function that counts how many characters, that is b. So what I should do is to take this input (regardless of length) and reverse the characters. Rysers example work just if you wrote the input in main.
So how can I use what I already have? I feel that I am really close, just that I get EDCDE instead of EDCBA:
void reverse(char a, int b)
for (int i = 0; i < 5; i=i++)
char temp1 = a[i];
a[(b-1)-i] = temp1;