nasm -f elf64 f.asm -o f.o
ld f.o -o f
- Instruction
A command for the CPU to perform certain actions. E.g.
mov - Transfer data from one register to another
int - Is used to generate Interrupt, mostly to request services from OS(Sys Calls)
- Register
A small storgae location in CPU, used to hold data and instructions temporarily.
There are two types,
- General Purpose
- Special Purpose
E.g.,
eax - Accumulator, Used to temporarily store results of computation.
ebx - Base pointer for memory access.
edx - I/O Operations, also holds intermediate results in arithmetic operations
(e.g. remainder of a division).
ecx - Used for data manipulation. Often used as a counter in loop and string manipulation.
- Directive
Assembler directives are special instructions in assembly language that provide guidance to the assembler on how to process the source code. E.g.,
data - Marks the beginning of a data segment where initialized data is defined.
text - Indicates the start of the code segment where executable instructions are located.
equ - Defines/assigns a constant value to a symbolic name
bss - Reserves space for uninitialized data.
org - Sets the origin or starting address for subsequent instructions or data.
- Common Conditional Jumps
je A, B ; Jump if equal
jne A, B ; Jump if not equal
jg A, B ; Jump if greater
jge A, B ; Jump if greater or equal
jl A, B ; Jump if less
jle A, B ; Jump if less or equal
- Stack
esp - Stack pointer, always points to the top of the stack in memory
- Common Data Types
db - Stores 1 byte
dw - Stores 2 bytes
dd - Stores 4 bytes