Apple IIe - Machine Language Programming Basics

The System Monitor 263
its card in peripheral slot #5. The computer could accept infor-
mation from the modem as well as information to it. By entering
the following commands, the computer would be instructed to
use the modem.
*5 CNTL-P
*5 CNTL-K
MACHINE LANGUAGE PROGRAMMING
Introduction
The process of writing a machine language program is a long and
tedious one compared to the process of writing a program in
BASIC. Why then would a programmer wish to write a program
in machine language? The answer is speed. Machine language
programs execute at a rate anywhere from 10to1000 times faster
than a BASIC program.
Mini-Assembler
An assembler greatly facilitates the process of writing a machine
language program. An assembler translates assembly language
mneumonics to operation codes which can be executed by the
microprocessor . Without an assembler, the programmer would
have to look up each operation code , one-by-one .
A
mneumonic is a short abbreviation for an assembly language
instructions. For
example, JSR is the mneumonic which stands
for the jump to subroutine operation. The microprocessor does
not understand mneumonics. It does however understand hex-
adecimal codes. The purpose of the assembler is to translate a
mneumonic (ex. JSR) to its equivalent hex value (#20).
The mini-assembler,
built into Integer BASIC, is not full-fledged
assembler. The mini-assembler does not support labels, nor does
it remember the source once return has been pressed. The
mini-assembler merely converts the mneumonic entered in the
command line into its equivalent hex value(s).