Apple II Monitor

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Last seen: 1 year 1 month ago
Joined: Jan 6 2022 - 20:12
Posts: 20
Apple II Monitor

Hiya folks,

When entering the Monitor mode, if I just hit the enter key repeatedly, it shows me this HEX data. Do you know what this data is?


What does B800, B808, B810 mean? What does "B" stand for? What is the actual HEX data? Is that the ROM code itself?


Moreover, when I press Control + E for "examine" it shows me the same text each time: 

A=FF X=98 Y=DS P=00 S=B7

What does A, X, Y, P and S stand for?

I'd very much like to make sense of the Monitor, but I don't know where to start.


Thanks everyone!



Last seen: 18 hours 47 min ago
Joined: Jun 25 2020 - 17:00
Posts: 237
What you are seeing is...


The 4 digit alphanumeric characters that start with "B" are the hexadecimal address values in the Apple's Read-Only-ROM memory.  The eight, two digit alphanumeric characters that follow each one of those is the 8-bit hexadecimal value of the data stored in the next eight memory locations.


The ROM "code" does not start until "C000", anything below that are contents in the dynamic RAM of the Apple.

Ctrl-E results in the display of the memory contents of the following 8-bit memory registers.  These registers are what the 6502 or 65C02 microprocessors uses in order for it to function as a computer processor.



X=X Register

Y=Y Register

P=Processor Register

S=Status Register


There are many great references that covers how the venerable Apple II works and here is one of them.  (Well I tried to upload the zip file of it but it won't do it.  I'll try later.)








Last seen: 1 year 1 month ago
Joined: Jan 6 2022 - 20:12
Posts: 20
LaserMaster ~ this is

LaserMaster ~ this is incredibly helpful. Both your explanation and the attachment, thank you. I've got my reading cut out for me :)

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