Art of Assembly Language, 1st Edition

4.8. 4.8 The HLA Standard Library CHARS.HHF Module

The HLA Standard Library chars.hhf module provides a couple of routines that convert characters from one form to another and several routines that classify characters according to their graphic representation. These functions are especially useful for processing user input to verify that it is correct.

The first two routines we will consider are the translation/conversion functions. These functions are chars.toUpper and chars.toLower. These functions use the following syntax:

chars.toLower( characterValue ); // Returns converted character in AL.
chars.toUpper( characterValue ); // Returns converted character in AL.

These two functions require a byte-sized parameter (typically an 8-bit register or ...