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base repository: yourtion/30dayMakeOS
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head repository: CodingdAwn/30dayMakeOS
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  • 6 commits
  • 4 files changed
  • 1 contributor

Commits on Oct 29, 2021

  1. record for day 1

    gaoxifeng committed Oct 29, 2021
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  2. record for day 1

    gaoxifeng committed Oct 29, 2021
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  3. note for day1 and day2

    gaoxifeng committed Oct 29, 2021
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  4. note for day1 and day2

    gaoxifeng committed Oct 29, 2021
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  5. some day 3 note

    gaoxifeng committed Oct 29, 2021
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Commits on Nov 5, 2021

  1. 提交笔记

    gaoxifeng committed Nov 5, 2021
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Showing with 92 additions and 0 deletions.
  1. +18 −0 01_day/readme.md
  2. +49 −0 02_day/readme.md
  3. +25 −0 03_day/readme.md
  4. 0 04_day/readme.md
18 changes: 18 additions & 0 deletions 01_day/readme.md
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## day 1

### 工具的使用
- asm.bat 执行汇编器 再生成一个img镜像
- run.bat 直接使用qemu虚拟机打开镜像文件

### 知识点
- 关键字使用大写或者小写都可以
- DB: data byte 写入一个字节
- DW: data word 2个字节
- DD: data double-word 4个字节
- ;用于注释
- $是当前已输出的字节数
- RESB: 填0
- boot sector: 启动区 软盘第一个扇区为启动区
512字节为一个扇区 软盘大小为1440KB 故有2880个扇区
启动区最后两个字节固定为 55 AA
- IPL: initial program loader
49 changes: 49 additions & 0 deletions 02_day/readme.md
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# day 2

## 知识点
- ORG: 指定程序起始位置
- JMP: jump
- entry: 只是标签 label 类似goto
- MOV: 赋值语句 MOV AX,0 即AX = 0, MOV源数据和目的数据位数相同
- ADD: 加法指令
- CMP: 比较指令
- JE: 比较跳转指令, 比较结果相等则跳转 否则继续执行下一条指令 jump if equal
- INT: 中断指令 INT 0x10 bios显卡指令
- BIOS: basic input output system
- HLT: cpu睡眠

### 寄存器:
16位寄存器
- AX -> accumulator 累加
- CX -> counter 计数
- DX -> data 数据
- BX -> base 基址
- SP -> stack pointer 栈指针
- BP -> base pointer 基址指针
- SI -> source index 源变址
- DI -> destination index 目的变址

8位寄存器
- AL,CL,DL,BL,AH,CH,DH,BH 分高低位

32位寄存器
- EAX,ECX,EDX,EBX,ESP,EBP,ESI,EDI

段寄存器 16位
- ES -> extra segment 附加段
- CS -> code segment 代码段
- SS -> stack segment 栈段
- DS -> data segment 数据段
- FS,GS

### 其他
[]为指定内存 cpu与内存的存取
- MOV WORD [678], 123 内存678-679 设置为123
- MOV BYTE [BX],123 内存[BX寄存器的值] 设置为123 {BX BP SI DI}可用

对于ORG 0x7c00的解释:
- 0x00007c00 -> 0x00007dff为 启动区内容装载地址
- 内存有部分地址是BIOS的地址

### 疑问
- $符号在ORG下 含义有变化？
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# day 3

## 知识点
- JC: jump if carry, 如果进位标记carry flag是1的话就跳转
- INT 0x13: 磁盘读写
- FLACS.CF: 进位标志 读写磁盘后进位标志会被设置
FLACS.CF为1位的寄存器
- JNC: jump if not carry 进位标记为0跳转
- JAE: jump if above or equal 如果大于或等于跳转
- JBE: jump if below or equal 如果小于或等于跳转
- JB: jump if below 如果小于就跳转
- EQU: 相当于#define CYLS EQU 10 ; CYLS=10

## 读写磁盘操作
- AH: 0x02读盘 0x03写盘 0x04校验 0x0c寻道
- AL: 扇区数
- CH: 柱面号&0xff
- CL: 扇区号
- DH: 磁头号 软盘有正反面2个磁头
- DL: 驱动器号 如果有多个软盘的话
- ES:BX 缓冲地址 从软盘中读取的数据装载到内存的哪个位置
MOV AL,[ES:BX] 标识ES*16+BX的内存地址 如果ES为0x20那么正好每次移动512个字节 即一个扇区..
如果指定内存的话 都必须同时指定 段寄存器 默认的话为DS: 可以省略
-

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