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:



regards

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.