microprocessor overview

[BogdanOntanu]

The values that overflow to the left of MSB are just lost.
ACtually the MSB bit will go into CARRY flag but it will be lost since we do not check it after that...
Usually XOR type of instructions clears the CARRY flag.

[t48605]

well , I ' m reading a book , at the part of introduction to 8088 microprocessor , till when they say that memory is divide into many parts such as part contains code program , part contains stack , child program ... and they talk about segment registers like code segment (CS) , data segment (DS) , stack segment (SS) and extra segment (ES) and their concern with memory ... I don't think I had understood it easily ?
Could you explain for me about that !
for example segment:offset
Thanks !!!

[asmfan]

in that old good time programs had block structure (code data stack). these blocks resided in memory area of 1MB and could be accessed through 20bit address. this address couldn't be accessed via only 16bit register (ax, dx...etc). but there were seament ones (cs, ds...) 16bit too. the address is calculated as such - segment:offset or [(segment shl 4) + offset] - the 20bit address. the segment is the base address of block of memory. offset itself

[asmfan]

for example if U would like to access the interrupt list in memory, which is 256*4 byte long and locates in 0:0 address, you need to set segment register to 0 and write the correct address in offset register. or, for example, if you need to access the 4h INT address (0:16 in memory) you can just set segment register to 1 and the offset register to 0 - you'll get the same 16 byte from the beginning.

[t48605]

well Thanks :)
now I 'm in troubles with bus , three kind : address bus , data bus , and control bus , all of them called system bus !
Could you give me some basically difference between them , especially in the amount of bit of them ?
thanks