Top "Instructions" questions

Questions about instructions of real CPUs, VMs or compiler IRs.

How exactly do executables work?

I know that executables contain instructions, but what exactly are these instructions? If I want to call the MessageBox API …

binary executable instructions
How does one change an instruction with a hex editor?

I am messing around with some reverse engineering, but I don't know how to change a jnz to jz with …

assembly hex reverse-engineering instructions ida
Use of TEST instruction with same register

Here is some C, found in a textbook I'm learning: ... do { ... n--; } while (n > 0) ... I assume n is at %…

assembly x86 x86-16 instructions
Assembly 64bit - movl, movq. Interchanging is okay?

Context: Learning GAS assembly on 64 bit linux. Many tutorials are for 32-bit assembly. Difficult to bushwhack through x86_64 assembly. Question: …

assembly 64-bit x86-64 gnu-assembler instructions
difference between conditional instructions (cmov) and jump instructions

I'm confused where to use cmov instructions and where to use jump instructions in assembly? From performance point of view: …

performance assembly instructions mov
What Do we mean by instruction size?

I am really consfused and may sound dumb question but I really not sure what does it mean when we …

assembly arm instructions instruction-set
How many asm-instructions per C-instruction?

I realize that this question is impossible to answer absolutely, but I'm only after ballpark figures: Given a reasonably sized …

c assembly instructions
JVM instruction ALOAD_0 in the 'main' method points to 'args' instead of 'this'?

I am trying to implement a subset of Java for an academic study. Well, I'm in the last stages (code …

java jvm bytecode instructions jasmin
Difference between memory and register

I saw assembly code like, MOV [EAX], EBX the above line, They are mentioned [EAX] is memory and EBX is …

memory assembly cpu-registers instructions mov