There are a few operations you can only do with DI/SI (or their extended counterparts, if you didn’t learn ASM in 1985). Among these are Which are, respectively, operations for repeated (= mass) storing, loading and scanning. What you do is you set up SI and/or DI to point at one or both operands, perhaps put a … Read more
Here is a pretty simple way to do it.
I was reading the following definition for syscall: I saw it explained that the line cmpq $-4095 %rax determines whether %rax contains a value between -1 and -4095. How does it do that? What exactly does the cmpq instruction do?
You have as input values. The instruction just subtracts 3(dec) in EDX from 100(hex) in EAX resulting in 100h-3h=0FDh.
You are not using the read string system call correctly. I suspect you haven’t actually looked at the documentation on how to use it. You have to pass two arguments: So you should do something like: Nevertheless, this shouldn’t cause a crash since $a0 should still hold the address of firstPromptString that you set up for the printing, earlier, and that … Read more
The two instructions load a constant of 0x05 into register $s0 and 0x07 into register $s1. MIPS doesn’t has an instruction that directly loads a constant into a register. Therefore logical OR with a operand of zero and the immediate value is is used as a replacement. It has the same effect as move. Translated … Read more
As has already been stated, wrapping brackets around an operand means that that operand is to be dereferenced, as if it were a pointer in C. In other words, the brackets mean that you are reading a value from (or storing a value into) that memory location, rather than reading that value directly. So, this: … Read more
General purpose means all of these registers might be used with any instructions doing computation with general purpose registers while, for example, you cannot do whatever you want with the instruction pointer (RIP) or the flags register (RFLAGS). Some of these registers were envisioned to be used for specific use, and commonly are. The most … Read more
Maybe you’re wondering about this: These lines are known as the assembly function prologue. The first 2 instructions save the previous base pointer (ebp) and set EBP to point at that position on the stack (right below the return address). This sets up EBP as a frame pointer. The sub esp,12 line is saving space … Read more
You are viewing SPIM registers in hex. Hexadecimal 10 is decimal 16.