CS208, Friday 21 Jan 2022

Coming up

• Monday assignment: bit operations & UTF-8
• Thursday assignment: questions about C & assembly language (posted by Monday)
• How does C get turned into assembly? assembly into machine?
• Debugging C programs with gdb

Questions?

Bitwise operations

• ~, &, |, ^, >>, <<
• | to turn a bit on
• & to turn a bit off ("masking")

• and grabbing pieces of a bit pattern

• assembling the integer you want

x86_64 architecture

x86_64 simple programs

We can write some simple programs in x86_64 assembly language.

Here's a hello-world program, along with an explanation how to assemble and run it: hello.asm

Mostly, we won't be writing assembly language programs. Instead, we'll be reading the assembly language generated by the gcc compiler.

Plan

• Learn some x86_64 basics
• Write small C programs and compile them to assembly
• Study the relationship between high-level language constructs (e.g. function-calling and parameter-passing, allocation of space for local variables, etc.) and their corresponding assembly language code