what do all these mean? (C and sourcer)

I quote this from a dissembled listing produced by sourcer. It is a C program.

¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó I/O Port Usage Synopsis  ¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó¡Ó

                                Port 0     : DMA-1 bas&add ch 0
                                Port 20h   : 8259-1 int      command
                                Port 20h   :  al = 20h,      end of interrupt
                                Port 40h   : 8253 timer      0 clock
                                Port 43h   : 8253 timer      control
                                Port 3F2h  : dsk0 contrl output







what do these mean?
whlukAsked:
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imladrisConnect With a Mentor Commented:
The disassembler is giving a rundown of the I/O ports that are being used and what they are used for:

Port 0: used to control DirectMemoryAccess channel 1
Port 20: The int command port of the Programmable Interrupt Controller
Port 20: Also used to signal End of Interrupt (at end of Interrupt routine) by sending a 20 to it
Port 40h   : used to get timer tick from the 8253 timer
Port 43h   : used to control 8253 timer
Port 3F2h  : used to control dsk0

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whlukAuthor Commented:
imtadris,
sorry, Could you please give me a more detailed descriptions on the above items? (cos' the manual doesn't talk about it very much and I also don't have any books for the above items. thanks in advance.

Regards,
Jacky
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lz_weiCommented:
everything is the interface of hardware. none can state it detailedly in a few word. you had batter get a book.
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whlukAuthor Commented:
Any good books to recommend?
Thanks
Jacky
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lz_weiCommented:
sorry, I am not in America. I am not familiar with such book of English version.
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