The Art of Assembly Language, 2nd Edition

4.13 Character Set Implementation in HLA

There are many different ways to represent character sets in an assembly language program. HLA implements character sets using an array of 128 boolean values. Each boolean value determines whether the corresponding character is a member of the character set; that is, a true boolean value indicates that the corresponding character is a member of the set, whereas a false value indicates that the character is not a member of the set. To conserve memory, HLA allocates only a single bit for each character in the set; therefore, HLA character sets consume 16 bytes of memory because there are 128 bits in 16 bytes. This array of 128 bits is organized in memory as shown in Figure 4-3.

Figure 4-3. Bit layout of a ...