Day 1

kernel.excalidraw

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KERNEL

APP

HARDWARE

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Interface = kernel. Kernel = controlling hardware by using its system calls lib that contains these system calls similar to opengl

envoke system call = kernel interupt program what performs the task of system call = driver

function number/OPCODE 1 = exit (1 arg) 4 = write (3 args)

EAX=1 → interupt → exit EAX=4 → interupt → write

EAX=4 usigned int fd = file descriptor → stdint stdout char *buf size_t count

SECTION .data
hw db 'Hello World', 0Ah

SECTION .text
global _start

_start:
    mov     edx, 12     ; size_t count
    mov     ecx, hw     ; char *buf
    mov     ebx, 1      ; unsigned int fd 
    mov     eax, 4      ; write
    int     80h