May 2014
Intermediate to advanced
320 pages
13h 41m
English
Content preview from Servicing Personal Computers, 3rd Edition
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
Start your free trial
130 Servicing Personal Computers
An example of embedding a machine language routine within a BASIC program is shown in
Listing 3.4. This program uses an array into which the machine code is loaded from a DATA
statement. The machine code uses the versatile Z80 LDIR instruction, which permits a block
transfer of memory. In this particular case, 512 bytes of memory, starting at an address
specified by the user, are transferred into the last 512 bytes of screen memory. This results in
the lower half of the screen being filled with ASCII and graphics characters which represent
the contents of the memory block in question. Typical screen dumps generate ...