Ive got an exam on computer architecture and assembly language, Im kinda stuck on understanding what status flags mean exactly! like MOVS or ADDS or ADDCS etc!

I would greatly appreciate it if someone could explain it to me!

thx

If the instruction is MOV, then the CPSR (Current Program Status Register) is not updated by the operation. If the instruction is MOVS, then the CPSR is updated. Similarly for other transfer and arithmetic/logic instructions.

The S in the source code causes bit 20 of the machine code instruction to be set, so the machine code follows the intent.

What is important about the CPSR? Well the CPSR flags N, Z, C, and V can be used by conditional branch instructions to direct program flow according to the results of the designated instructions. Or, carry out of one instruction can be used in the operation of certain subsequent operations. Stuff like that.


Regards,

Dave