PLEASE EXPLAIN THIS PROBLEM:

Let TOUPPER be the following macro:

#define TOUPPER(c) ('a'<=(c)&&(c)<='z'?(c)-'a'+'A':(c))

Let s be a string and let i be an int variable. Show the output produced by each of the following program fragments.

(a)

strcpy(s, "abcd"); i = 0; putchar(TOUPPER(s[++i]));

(b)

strcpy(s, "0123"); i = 0; putchar(TOUPPER(s[++i]));