nsadisha

Principle	Description
Single Responsibility Principle (SRP)	A class should have only one reason to change, or in other words, it should have a single responsibility.
Open-Closed Principle (OCP)	Software entities should be open for extension, but closed for modification.
Liskov's Substitution Principle (LSP)	An object of super class can be replaced with an object of a sub class without altering the correctness of the program.
Interface Segregation Principle (ISP)	Using Many task specific interfaces is better than one general purpose interface
Dependency Inversion Principle (DIP)	High-level modules should not depend on low-level modules. Both should depend on abstraction. Abstraction should not depend on details. Details should depend on abstraction.

nsadisha

ENTRY(loader)                /* the name of the entry label */

SECTIONS {
    . = 0xC0100000;          /* the code should be relocated to 3GB + 1 MB */

    kernel_virtual_start = .;
    kernel_physical_start = . - 0xC0000000;

    /* align at 4 KB and load at 1 MB, AT specifies load address */
    .text ALIGN (0x1000) : AT(ADDR(.text)-0xC0000000)

nsadisha

    OBJECTS = loader.o kmain.o
    CC = gcc
    CFLAGS = -m32 -nostdlib -nostdinc -fno-builtin -fno-stack-protector \
             -nostartfiles -nodefaultlibs -Wall -Wextra -Werror -c
    LDFLAGS = -T link.ld -melf_i386
    AS = nasm
    ASFLAGS = -f elf

    all: kernel.elf

nsadisha

    global loader                   ; the entry symbol for ELF
    extern sum_of_three

    MAGIC_NUMBER equ 0x1BADB002     ; define the magic number constant
    FLAGS        equ 0x0            ; multiboot flags
    CHECKSUM     equ -MAGIC_NUMBER  ; calculate the checksum
                                    ; (magic number + checksum + flags should equal 0)

    section .text:                  ; start of the text (code) section
    align 4                         ; the code must be 4 byte aligned

nsadisha

    megs:            32
    display_library: sdl
    romimage:        file=/usr/share/bochs/BIOS-bochs-latest
    vgaromimage:     file=/usr/share/bochs/VGABIOS-lgpl-latest
    ata0-master:     type=cdrom, path=os.iso, status=inserted
    boot:            cdrom
    log:             bochslog.txt
    clock:           sync=realtime, time0=local
    cpu:             count=1, ips=1000000

nsadisha

    default=0
    timeout=0

    title os
    kernel /boot/kernel.elf

nsadisha

ENTRY(loader)                /* the name of the entry label */

SECTIONS {
    . = 0x00100000;          /* the code should be loaded at 1 MB */

    .text ALIGN (0x1000) :   /* align at 4 KB */
    {
        *(.text)             /* all text sections from all files */
    }

nsadisha

    global loader                   ; the entry symbol for ELF

    MAGIC_NUMBER equ 0x1BADB002     ; define the magic number constant
    FLAGS        equ 0x0            ; multiboot flags
    CHECKSUM     equ -MAGIC_NUMBER  ; calculate the checksum
                                    ; (magic number + checksum + flags should equal 0)

    section .text:                  ; start of the text (code) section
    align 4                         ; the code must be 4 byte aligned
        dd MAGIC_NUMBER             ; write the magic number to the machine code,