OSI好多層層層層層層層

7層

OSI model 維基百科

積項之和/和項之積

• 積項之和（Sun of Products，SOP）

ABC + ABC
AB + ABC + C D + D
AB + CD + EF + GK + HL

由一個或一個以上的AND項互相OR在一起
所組成

• 和項之積（Product of Sums，POS）

(A+ B +C)(A+C)
(A + B)(C + D)F
(A+C)(B + D)(B +C)
由一個或一個以上的OR項，AND在一
起所構成

• 布林代數與基本邏輯閘

英國數學家 George Boole 在 1854 年提出一套數學系統，來解決分析與設計數位電路之方
法，稱為布林代數 (Boolean Algebra)。

為了分析與設計數位系統，德國數學家 C. E. Shannon，在 1938 年發展一套兩值布林代數，
又被稱為交換代數 (Switching Algebra)，並證明兩值布林代數，可充分代表數位系統之特性，
因此兩值布林代數已被發展成為數位系統分析與設計之數學基礎。



一、布林代數之性質

布林代數與一般演繹性之代數系統一樣，它亦可用一組基本元素之集合、一組運算子與許多未證明之定理與假設來定義。

‹ 

布林代數可用下式來表示

B = f (w, x, y,z, ... )

其中 B 為輸出變數w、 x、 y、z等輸入變數之函數，即 B 之值是由w、 x、 y、z

等變數來決定。

‹

構成布林代數之基本元素，僅被允許為 0 與 1 兩個可能元素之一，且所有數位系統之輸入與輸出變數，亦僅被限制為 0 與 1 兩個可能邏輯值之一，而這兩個邏輯值 (0 與 1)  是分別用來代表數位系統之低電位與高電位的電壓位準，故足以說明布林代數與數位系統間之直接對應關係。

     

二、布林代數之定義

兩值布林代數之輸入與輸出變數僅允許 0 與 1 兩個元素，因組成布林代數為此兩元素，即

B ={0,1}集合，與 AND (  積；．)、OR (  和；+ )  與 NOT (  反； )  三個基本二元邏輯運算

子 (Binary Logic Operator)  所組成之代數架構。

‹ 布林代數亦應是一套完整之代數系統，故布林代數 B 應為 0 與 1 等兩值所組成之集合，即

B = {0,1}，因此對於 B 中之所有元素，應滿足下列六項基本假設：

1. 封閉性(Closure Properties)：對集合 B 中的任一個元素而言，經二元運算子運算後所得到

    之元素，亦應為集合 B 之元素。

2. 單位元素 (Identity Unit)：若集合 B 存在一個 0 或 1 之元素，則經邏輯運算後，會滿足

    x ⋅1 = 1⋅ x = x與 x + 0 = 0 + x = x。

3. 交 換 律 (Commutative Law)：對任意兩個元素x, y ∈ B 而言，若存在交換律，則應滿足

    x ⋅ y = y ⋅ x與 x + y = y + x。

4. 分配律 (Distributive Law)：對任意三個元素 x, y,z ∈ B而言，若存在分配律，則應滿足

    x ⋅( y + z) = x ⋅ y + x ⋅z與 x + ( y ⋅z) = (x + y)⋅(x + z)。

5. 反元素 (Inverse Element)：對集合 B 中的任一個元素而言，若存在x ∈ B，亦存在 x ∈ B。

6. 布林代數 B 至少存在兩個不同之元素x ⋅ y∈ B，且 x ≠ y，即兩值布林代數有兩個元素 1

與 0，且1 ≠ 0。

                                            

                                                證明假說(4)之真值表

三、布林代數之基本定理

接著列出許多常用之布林定理，並分為單變數與多變數兩個部分來討論如下：

1.  單變數布林定理

2. 多變數布林定理

狄摩根定律 (DeMorgan’s Theorem)  之變數，亦可適用於 n 個變數之布林代數式，即下面之布林等式亦可成立，即

(a)  x + y + ...+ n = x ⋅ y ⋅ ... ⋅n

(b) x ⋅ y ⋅ ... ⋅n = x + y + ... + n

CH7:儲存體

Memory address register(MAR)

The Memory Address Register (MAR) is a CPU register that either stores the memory address from which data will be fetched to the CPU or the address to which data will be sent and stored.

 

Memory buffer register(MBR)

A Memory Buffer Register (MBR) is the register in a computer's processor, or central processing unit, CPU, that stores the data being transferred to and from the immediate access store. It acts as a buffer allowing the processor and memory units to act independently without being affected by minor differences in operation. A data item will be copied to the MBR ready for use at the next clock cycle, when it can be either used by the processor or stored in main memory.

Program counter (PC)

The program counter (PC), commonly called the instruction pointer (IP) in Intel x86 and Itanium microprocessors, and sometimes called the instruction address register (IAR)or just part of the instruction sequencer, is a processor register that indicates where a computer is in its program sequence.






Cloud storage
Cloud storage is a model of networked online storage where data is stored in virtualized pools of storage which are generally hosted by third parties. Hosting companies operate large data centers, and people who require their data to be hosted buy or lease storage capacity from them. The data center operators, in the background, virtualize the resources according to the requirements of the customer and expose them as storage pools, which the customers can themselves use to store files or data objects. Physically, the resource may span across multiple servers.
Cloud storage services may be accessed through a web service application programming interface (API), or through a Web-based user interface.

Column Address Strobe (CAS)


Column Address Strobe (CAS) latency, or CL, is the delay time between the moment a memory controller tells the memory module to access a particular memory column on a RAM memory module, and the moment the data from given array location is available on the module's output pins. In general, the lower the CAS latency, the better.





IP(Instruction pointer)

An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication.[1] An IP address serves two principal functions: host or network interface identification and location addressing. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there.
In most processors, PC is incremented after fetching an instruction, and holds the memory address of (“points to”) the next instruction that would be executed. (In a processor where the incrementation precedes the fetch, PC points to the current instruction being executed.)
Instructions are usually fetched sequentially from memory, but control transfer instructions change the sequence by placing a new value in PC. These include branches (sometimes called jumps), subroutine calls, and returns. A transfer that is conditional on the truth of some assertion lets the computer follow a different sequence under different conditions.
A branch provides that the next instruction is fetched from somewhere else in memory. A subroutine call not only branches but saves the preceding contents of PC somewhere. A return retrieves the saved contents of PC and places it back in PC, resuming sequential execution with the instruction following the subroutine call.




ROM (Read-only memory)

Read-only memory (ROM) is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware (software that is very closely tied to specific hardware, and unlikely to need frequent updates).
In its stric⋯⋯test sense, ROM refers only to mask ROM (the oldest type of solid state ROM), which is fabricated with the desired data permanently stored in it, and thus can never be modified. Despite the simplicity, speed and economies of scale of mask ROM, field-programmability often make reprogrammable memories more flexible and inexpensive. As of 2007[update], actual ROM circuitry is therefore mainly used for applications such as microcode, and similar structures, on various kinds of processors.
Other types of non-volatile memory such as erasable programmable read only memory (EPROM) and electrically erasable programmable read-only memory (EEPROM or Flash ROM) are sometimes referred to, in an abbreviated way, as "read-only memory" (ROM); although these types of memory can be erased and re-programmed multiple times, writing to this memory takes longer and may require different procedures than reading the memory.[1] When used in this less precise way, "ROM" indicates a non-volatile memory which serves functions typically provided by mask ROM, such as storage of program code and nonvolatile data.
ROM is also useful for binary storage of cryptographic data, as it makes them difficult to replace, which may be desirable in order to enhance information security.
Read-only memory (Read-Only Memory, ROM) is a semiconductor memory, and its characteristics once the stored data can no longer change or delete the content will not disappear because the power is turned off.Require frequent changing programs or data in electronic or computer system, usually used to store.




Cache memory
A CPU cache is a cache used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations. As long as most memory accesses are cached memory locations, the average latency of memory accesses will be closer to the cache latency than to the latency of main memory.


NAS(Network-attached storage)

Network-attached storage (NAS) is file-level computer data storage connected to a computer network providing data access to heterogeneous clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements. NAS is often made as a computer appliance – a specialized computer built from the ground up for storing and serving files – rather than simply a general purpose computer being used for the role.

RAS(Row Address Stobe)

Abbreviated RAS, a signal, or strobe, sent by the processor to a DRAM circuit to activate a row address. DRAM stores data in a series of rows and columns, similar in theory to a spreadsheet, and each cell where a data bit is stored exists in both a row and a column. A processor uses RAS and CAS (column address strobe) signals to retrieve data from DRAM. When data is needed, the processor activates the RAS line to specify the row where the data is needed, and then activates the CAS line to specify the column. Combined, the two signals locate the data stored in DRAM.

CH4:系統單元的組成原件

Motherboard

In personal computers, a motherboard is the central printed circuit board (PCB) in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals.



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Central processing unit(CPU)

The central processing unit (CPU) is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The form, design and implementation of CPUs have changed dramatically since the earliest examples, but their fundamental operation remains much the same. Two typical components of a CPU are the arithmetic logic unit (ALU), which performs arithmetic and logical operations, and the control unit (CU), which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.
Control unit(CU)

A control unit in general is a central (or sometimes distributed but clearly distinguishable) part of the machinery that controls its operation, provided that a piece of machinery is complex and organized enough to contain any such unit. One domain in which the term is specifically used is the area of computer design. In the automotive industry, the control unit helps maintain various functions of the motor vehicle.

Arithmetic logic unit(ALU)

In computing, an arithmetic logic unit (ALU) is a digital circuit that performs arithmetic and logical operations. The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers. The processors found inside modern CPUs and graphics processing units (GPUs) accommodate very powerful and very complex ALUs; a single component may contain a number of ALUs

Bus (computing)
In computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.

Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same logical functionality as a parallel electrical bus. Modern computer buses can use both parallel and bit serial connections, and can be wired in either a multidrop (electrical parallel) or daisy chain topology, or connected by switched hubs, as in the case of USB.

Volatile memory
Volatile memory, also known as volatile storage, is computer memory that requires power to maintain the stored information, unlike non-volatile memory which does not require a maintained power supply. It has been less popularly known as temporary memory.
Most forms of modern random-access memory (RAM) are volatile storage, including dynamic random-access memory (DRAM) and static random-access memory (SRAM). Content addressable memory and dual-ported RAM are usually implemented using volatile storage. Early volatile storage technologies include delay line memory and Williams tube.

Non-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM (F-RAM), most types of magnetic computer storage devices (e.g. hard disks, floppy disks, and magnetic tape), optical discs, and early computer storage methods such as paper tape and punched cards.


Expansion slot (Adapter card)
The expansion card (also expansion board, adapter card or accessory card) in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard or backplane to add functionality to a computer system via the expansion bus.

Sound card

A sound card (also known as an audio card) is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware inside the PC.

Video card

A video card, display card, graphics card, or graphics adapter is an expansion card which generates a feed of output images to a display. Most video cards offer various functions such as accelerated rendering of 3D scenes and 2D graphics, MPEG-2/MPEG-4 decoding, TV output, or the ability to connect multiple monitors (multi-monitor).

Memory Stick (Removable flash memory)

In addition to the original Memory Stick, this family includes the Memory Stick PRO, a revision that allows greater maximum storage capacity and faster file transfer speeds; Memory Stick Duo, a small-form-factor version of the Memory Stick (including the PRO Duo); and the even smaller Memory Stick Micro (M2).





Power supply unit (computer)
For electronic power supplies in general, not just used in desktop computer devices or computer server devices, see Power supply.
A power supply unit (PSU) converts mains AC to low-voltage regulated DC power for the internal components of the computer. Modern personal computers universally use a switched-mode power supply. Some power supplies have a manual selector for input voltage, while others automatically adapt to the supply voltage.

Connector

An electrical connector is an electro-mechanical device for joining electrical circuits as aninterface using a mechanical assembly. The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or devices.

Keying

Many connectors are keyed , with some mechanical component which prevents mating except with a correctly-oriented matching connector.This can be used to prevent incorrect or damaging interconnections, either preventing pins from being damaged by being jammed in at the wrong angle or fitting into imperfectly fitting plugs, or to prevent damaging connections, such as plugging an audio cable into a power outlet.    

Plug and socket connectors

Plug and socket connectors are usually made up of a male plug (typically pin contacts) and a female receptacle (typically socket contacts), although hermaphroditic connectors exist, such as the original IBM token ring LAN connector. Plugs generally have one or more pins or prongs that are inserted into openings in the mating socket. The connection between the mating metal parts must be sufficiently tight to make a good electrical connection and complete the circuit. When working with multi-pin connectors, it is helpful to have a pinout diagram to identify the wire or circuit node connected to each pin.

8P8C connector

8P8C is short for "eight positions, eight conductors", and so an 8P8C modular connector (plug or jack) is a modular connector with eight positions, all containing conductors. The connector is probably most famous for its use in Ethernet and widely used on CAT5 cables.

D-subminiature connectors

The D-subminiature electrical connector is commonly used for the RS-232 serial port on modemsand IBM compatible computers. The D-subminiature connector is used in many different applications, for computers, telecommunications, and test and measurement instruments. A few examples are monitors ( MGA , CGA , EGA ), the Commodore 64 , MSX , Apple II , Amiga , andAtari joysticks and mice, and game consoles such as Atari and Sega .

USB connectors

The Universal Serial Bus is a serial bus standard to interface devices, founded in 1996. It is currently widely used among PCs , Apple Macintosh and many other devices. There are several types of USB connectors, and some have been added as the specification has progressed. The most commonly used is the (male) series "A" plug on peripherals , when the cable is fixed to the peripheral. If there is no cable fixed to the peripheral, the peripheral always needs to have a USB "B" socket. In this case a USB "A" plug to a USB "B" plug cable would be needed. USB "A" sockets are always used on the host PC and the USB "B" sockets on the peripherals. It is a 4-pin connector, surrounded by a shield. There are several other connectors in use, the mini-A, mini- B and mini-AB plug and socket (added in the On-The-Go Supplement to the USB 2.0 Specification).

Power connectors

Power connectors must protect people from accidental contact with energized conductors. Power connectors often include a safety ground connection as well as the power conductors. In larger sizes, these connectors must also safely contain any arc produced when an energized circuit is disconnected or may require interlocking to prevent opening a live circuit.

DC connectors

A DC connector is an electrical connector for supplying direct current (DC) power. For portable consumer electronic devices, the coaxial power connector is frequently used, but many other types of connectors also exist.

Radio frequency connectors

A radio-frequency connectormust not allow external signals into the circuit, and must prevent leakage of energy out of the circuit. At lower radio frequencies simple connectors can be used with success, but as the radio frequency increases, transmission line effects become more important, with small impedance variations from connectors causing the signal to reflect from the connector, rather than to pass through. At UHF and above, silver-plating of connectors is common to reduce losses.For Wi-Fi antennas the R-TNC connectors are used. A BNC connector is common for radio and test equipment used up to about 1 GHz.

Hybrid connectors

Hybrid connectors have housings with inserts that allow the intermixing of many connector types, such as those mentioned above. These housings may also allow intermixing of electrical and non-electrical interfaces, examples of the latter being pneumatic line connectors, andoptical fiber connectors . Because hybrid connectors are modular in nature, they tend to simplify assembly, repair, and future modifications.They also allow the creation of composite cable assemblies that can reduce equipment installation time by reducing the number of individual cable and connector assemblies.