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A Look at the
Sample Program
Note
If you have properly completed steps above, you should be able to hit
<RETURN> (or <ENTER> on some keyboards) and get a prompt on
your terminal screen.
If you do not see any prompt, retrace your steps through the hardware
and software installation procedures outlined in the manuals above,
verifying all connections and procedural steps. In any case, you must
have a command prompt on your terminal screen before proceeding
with the tutorial.
The sample program "COMMAND_READER" used in this chapter is
shown Figure 2-2. The program emulates a primitive command
interpreter.
This sample program is written for Mitsubishi RASM77 Assembler.
Data Declarations
INPUT_POINTER and OUTPUT_POINTER define the address
locations of an input area and an output area to be used by the program.
MESSAGE_A, MESSAGE_B and INVALID_INPUT are the messages
used by the program to respond to various command inputs.
Initialization
First, the INIT routine set up the stack pointer. Next, locations of the
input area is cleared by the CLEAR_INPUT routines.
READ_INPUT
This routine continuously reads the byte at location 100 hex until it is
something other than a null character (00 hexadecimal); when this
occurs, the CLEAR_OUTPUT routine clears the output area, and the
PROCESS_COMM routine is executed.
Getting Started 2-3
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