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pc2



Joined: 09 Feb 2005
Posts: 3
Location: Brazil
pc2
we are assembly beginners and we are already programming with i/o in DOS, we know that ":" is a label indicator, but we would like to know what does "register:register" mean, for example:

Code:
DS:[...]    


regards

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Paulo Marcos Durand Segal & Claudio Marcos Durand Segal
Post 09 Feb 2005, 14:10
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asmdemon



Joined: 18 Jan 2004
Posts: 97
Location: Virginia Beach, VA
asmdemon
When in DOS, the mode the processor is in is usually real mode. (this is apposed to Protected mode) While in real mode code and data access is done by segment registers(CS, DS, ES, FS, GS, SS) and a data indicating the offset (IP, AX, BX, CX, DX, SP, BP ...). These 2 registers linked to gether, ie CS:IP, indicates the location in memory you are trying to reference. To calculate the actual address, multiply the Segment register by 16d (0x10, 10h) and then add the offset. Therefore, 07C0:0000 is equal to 0000:7C00 because they both reference the same location in memory (0x07C00). I hope this answers your question.
Post 09 Feb 2005, 14:25
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
Post 09 Feb 2005, 23:07
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