MEMORY WINDOW
A byte-sized look at your Atari memory
SYNOPSIS
This program lets you view any portion of your computer's memory on the screen. It runs on all Atari computers, and requires 16K RAM and BASIC. A joystick is optional.
If you've ever wondered what the inside of your computer's memory looks like, this program may help satisfy your curiosity by opening a window for you directly into memory.
HOW TO USE THE PROGRAM
When you first RUN the program, the screen is split horizontally into two areas. The upper half of the screen contains a Graphics 0 text screen which holds eight lines of 32 characters each--exactly enough to display 256 characters, or one page of memory. The bottom half of the screen shows which memory locations (in decimal form) are on display, and the number of the current page of memory.
The initial display starts at the location of the Graphics 0 text screen you see when you turn on the computer. As a result, you'll see the message "Current Memory = " and the location numbers flashing on both halves of the split screen. You can use the keyboard or a joystick to move the display through memory.
Pressing [.] or the joystick button resets you to Page Zero. If you press [>] or push the joystick forward, the window moves forward through memory one page at a time. If you press [<] or pull the joystick back, you'll move backwards through memory. Bytes in memory are displayed as their internal Atari-character-set equivalents. Use the up arrow or the down arrow, or push the joystick right or left to move through memory one byte at a time.
HOW THE PROGRAM WORKS
The program changes the address of screen memory in the display list according to input from the joystick or keyboard. The [BREAK] key is disabled, so you must either press [RESET] or reboot to end the program.
PROGRAM TAKE APART
Line 70: TRAPs to a RUN command, disables [BREAK], sets screen margins.
Line 80: Disables cursor, sets narrow (32-column) playfield.
Line 9O: POKEs new display list (DL) into Page Six from DATA statements.
Lines 100-150: Set up new DL and activate it.
Lines 160-170: Print current memory and page values.
Lines 180-220: Accept joystick and keyboard input.
Line 230: Restricts input range to actual memory locations.
Lines 240-260: Adjust DL to display new memory range and to branch back to display and input routine.
Dave Mentley is a consultant in the area of flatpanel displays. He uses the Atari 800 for report writing and data base maintenance. Dave is a former president of ABACUS, an Atari Users' Group in San Francisco.
Listing: MEMWINDO.BAS Download