Why is %c used in C?

Question

According to K&R C section 1.6, a char is a type of integer. So why do we need %c. And why can't we use %d for everything?

Answer 1

Because %d will print the numeric character code of the char:

printf("%d", 'a');

prints 97 (on an ASCII system), while

printf("%c", 'a');

prints a.

Answer 2

While it's an integer, the %c interprets its numeric value as a character value for display. For instance for the character a:

If you used %d you'd get an integer, e.g., 97, the internal representation of the character a

vs

using %c to display the character 'a' itself (if using ASCII)

I.e., it's a matter of internal representation vs interpretation for external purposes (such as with printf)