good question. If you have to ask "when should inline assembly" be used. chances are you don't have a situation that require the use of it. It is commonly used in embedded systems development, operating system development, etc. to do things that your higher level language can't to easily. for example. If I am making a simple kernel in C and I need have a function to call the bios video interrupt. I could do something like this. void CallVideoInterrupt() { -----__asm -----{ ----------mov ah,0 ----------int 0x10 -----} } so I guess one of the main uses for it is to expose low level functionality that you main high level language ( C/C++ ) doesn't have.