Data Organization
1. 进制转换。
按照正常的书写顺序写一个数字(无论多少进制),其中最左边的列称为“最高有效符号”,最右边的列称为“最低有效符号”。
(The right-most column is called
the least significant symbol, and the left-most column is called
the most significant symbol.)
二进制、十进制与十六进制转换表,学过数电一定对这个很熟悉~
![](https://yqfile.alicdn.com/img_8a418ee4871bc44063a9cc192fdb0554.png?x-oss-process=image/resize,w_1400/format,webp)
2. Data sizes
在存储
多字节数据时,有“大端法”和“小端法”两种模式,区别在于把放置“最高有效符号”和“最低有效符号”的顺序。
(Computers differ in how they organize multiple-byte values. Some of them use
big-endian ordering and put the most significant byte of the number in the first storage byte, and others use
little-endian ordering and put the least significant byte of the number in the first storage byte.)
二者的区别可从这张图上很直观的看出来
![](https://yqfile.alicdn.com/img_a766121f89d9f32c32a161fbad0cf179.png?x-oss-process=image/resize,w_1400/format,webp)
3. 字符编码
为了存储非数值类型的数据(字符),我们以各种标准来编码字符,比如ASCII和Unicode
(...to stores letters and sentences. The most common technique is to encode the characters
using ASCII or Unicode.)
ASCII码由于只占一个字节,因此不受大小端模式的影响。
(The endian ordering of a system does not play a role in how the characters are stored because these are separate 1-byte values.)
4. 数据结构
数据结构描述了数据的布局(或者我理解为一种协议),程序根据这些约定好的布局,访问特定数据域得到目标值。
(Computers know the layout of the data because of data structures.
A data structure describes how data are laid out. It works like a template or map.
The data structure is broken up into
fields, and each field has a size and name, although this information is not saved with the
data.)
5. 标志位
有时需要的信息是二值的,一个位即可存储,然而计算机的最小存储单位是字节,这时可把若干位组合成一个字节,每一位称作一个标志位。
(这时各种强大的位运算可以大显身手了~)
(A more efficient
method is to pack several of these binary conditions into one value. Each bit in the value
corresponds to a feature or option.)
Booting Process
下图虚线描述了计算机通电后控制权的转交过程,即BIOS->MBR->VBR->OS中的引导代码
![](https://yqfile.alicdn.com/img_216119b600e13830839fbe8dd74fc5d4.png?x-oss-process=image/resize,w_1400/format,webp)