Machine Language Program Control Statements - Sharp MZ-700 Owner's Manual

2.8
Machine Language Program Control
Statements
Several machine language program control statements are suported by the MZ-700 BASIC interpreter.
With these statements, machine language programs can be linked with a BASIC program.
Computer programming languages form a hierarchical structure as shown below. High level languages such
as BASIC automatically performs work required when lower level languages such as assembly language are
used. Although high level languages are convenient and easy to use, they cannot control the CPU directly.
The lowest level language (machine language) directly controls the CPU and provides high processing
speed, but considerable skill is required for coding long programs.
Machine language program control statements enable sophisticated programming techiques which make it
possible to utilize the advantages of both BASIC and machine language.
Machine language programs can be generated and loaded into the machine language program area (reserved
with the BASIC LIMIT statement) using the monitor or assembler and loader. Such machine language
programs can be called by BASIC programs with- the USR ( ) function. Machine language programs
can also be loaded into memory using a BASIC program which uses the POKE statement to write each
step in machine code. the resultant machine language program can then be called by BASIC programs
with the USR ( ) function.
The memory map at bottom right outlines the concept of data access with POKE and PEEK, and of
calling machine language programs with USR ( ).
$0000 r---------------------,
US R
C$ 8 000)
SYS TEM
BASIC program
POKE PEEK
LIMIT
~b-...--r....,..-,-+-....,......,-,-T--7---r-?"--r-7-r-;"""'7K
$ A F F F
Machine language
program area
All RAM in the
700 mode
------------------------------------------------------------~----------91