2023-09-12 02:42 作者:MochiCruise 围观:


Floating Point

Floating-point numbers are a data type used in computer programming that stores a number with a floating decimal point. A decimal point "floats" when its position is not fixed in place by the number format. For example, 3.145, 12.99, and 234.9876 are all floating-point numbers since the decimal point is not always in the same position.

A computer stores a floating-point number by breaking it into two parts. The first is called the "significand" or "mantissa," which stores the significant digits as a whole number value without a decimal point. The second is the "exponent," which modifies the magnitude of the significand by setting the position of the decimal point. Multiplying the significand by the exponent produces the final value. Some floating-point number formats use a base-10 exponent, while others use a base-2 exponent. For example, storing the number 4.7988 as a floating-point number would use the significand "47988" and the exponent

Computer programming languages store numbers without decimal points (called integers) as a separate number format. Some languages also support fixed-point numbers, which fix the decimal point in the same place for every number — for example, currency values that always have two digits after a decimal point. Mathematical calculations using integers or fixed-point numbers are less computationally expensive, so using those options when possible is more efficient than using floating-point numbers for everything.

NOTE: Older computer CPUs like the Intel 80386 and the Motorola 68000 series lacked hardware support for floating-point operations, slowly performing them in software instead. These chips used a companion processor, called a floating point unit (FPU) or "math coprocessor," to take over floating-point operations and significantly improve performance. Modern processors include support for floating-point operations without a coprocessor.


Computer Science 计算机科学

Technical Terms 技术术语 ; 专业术语

Floating Point 浮点 ; 浮点数

number with 带有的数字 ; 把…包括进

floating decimal 浮点十进制

decimal point 小数点

same position 位置

mantissa [mænˈtɪsə] 尾数,小数部分

floating-point number 浮点数 ; 浮点数值 ; 浮点数表示法

significant digits 有效数字 ; 有效位数 ; 有效数字位数

exponent [ɪkˈspoʊnənt] 指数(幂)。比如 4.7988 = 47988 * 读作 10 负 4 次方或 10 的 负 4 次幂,其中 的 英文读法为:10 to the negative 4th power




注:像Intel 80386和Motorola 68000系列这样的老式计算机CPU缺乏对浮点运算的硬件支持,只能在软件中缓慢执行。这些芯片使用了一种称为浮点单元(FPU)或“数学协处理器”的配套处理器来接管浮点运算并显著提高性能。现代处理器支持无需协处理器的浮点运算。


Binary (or base-2) a numeric system that only uses two digits — 0 and 1. Computers operate in binary, meaning they store data and perform calculations using only zeros and ones.

A single binary digit can only represent True (1) or False (0) in boolean logic. However, multiple binary digits can be used to represent large numbers and perform complex functions. In fact, any integer can be represented in binary.

One bit contains a single binary value — either a 0 or a 1. A byte contains eight bits, which means it can have 256 (28) different values. These values may be used to represent different characters in a text document, the RGB values of a pixel within an image file, or many other types of data.

Large files may contain several thousand bytes (or several megabytes) of binary data. A large application may take up thousands of megabytes of data. No matter how big a file or program is, at its most basic level, it is simply a collection of binary digits that can be read by a computer processor.

NOTE: The term "binary" may also be used to describe a compiled software program. Once a program has been compiled, it contains binary data called "machine code" that can be executed by a computer's CPU. In this case, "binary" is used in contrast to the text-based source code files that were used to build the application.


megabytes 兆字节,即 MB







Stands for "Virtual Local Area Network," or "Virtual LAN." A VLAN is a custom network created from one or more existing LANs. It enables groups of devices from multiple networks (both wired and wireless) to be combined into a single logical network. The result is a virtual LAN that can be administered like a physical local area network.

In order to create a virtual LAN, the network equipment, such as routers and switches must support VLAN configuration. The hardware is typically configured using a software admin tool that allows the network administrator to customize the virtual network. The admin software can be used to assign inpidual ports or groups of ports on a switch to a specific VLAN. For example, ports 1-12 on switch #1 and ports 13-24 on switch #2 could be assigned to the same VLAN.

Say a company has three pisions within a single building — finance, marketing, and development. Even if these groups are spread across several locations, VLANs can be configured for each one. For instance, each member of the finance team could be assigned to the "finance" network, which would not be accessible by the marketing or development teams. This type of configuration limits unnecessary access to confidential information and provides added security within a local area network.

VLAN Protocols

Since traffic from multiple VLANs may travel over the same physical network, the data must be mapped to a specific network. This is done using a VLAN protocol, such as IEEE 802.1Q, Cisco's ISL, or 3Com's VLT. Most modern VLANs use the IEEE 802.1Q protocol, which inserts an additional header or "tag" into each Ethernet frame. This tag identifies the VLAN to which the sending device belongs, preventing data from being routed to systems outside the virtual network. Data is sent between switches using a physical link called a "trunk" that connects the switches together. Trunking must be enabled in order for one switch to pass VLAN information to another.

4,904 VLANs can be created within an Ethernet network using the 802.1Q protocol, but in most network configurations only a few VLANs are needed. Wireless devices can be included in a VLAN, but they must be routed through a wireless router that is connected to the LAN.





由于来自多个VLAN的流量可能在同一物理网络上传输,因此必须将数据映射到特定网络。这是使用VLAN协议完成的,例如IEEE 802.1Q、Cisco的ISL或3Com的VLT。大多数现代VLAN使用IEEE 802.1Q协议,该协议在每个以太网帧中插入一个额外的报头或“标签”。此标签标识发送设备所属的VLAN,防止数据路由到虚拟网络之外的系统。数据在交换机之间使用称为“中继”的物理链路进行发送,该链路将交换机连接在一起。必须启用中继,一个交换机才能将VLAN信息传递给另一个交换机。