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Contents: Introduction to computer systems, basic components of a computer, computer hardware major technical indicators
Dry start
1.1 Introduction to computer systems
hardware and software concept of a computer's
The computer system is composed of "hardware" and "software" two major components
Hardware: things solid portion of the computer, which is made visible and tangible variety of electronic components, various types of optical, electrical, mechanical equipment composition, such as the host, such as peripheral devices
Software: invisible, the program has various special features of the composition prepared in advance people
Computer performance will depend on the "soft" and "hard" member function of the sum of
Computer software generally can be divided into two categories: system software and application software
System Software: also known as system programs, mainly used to manage the entire computer system, supervisor service, the system resources will be called, efficient operation.
System software includes: standard libraries, language processing program (such as assembly language translated into machine language or assembler to translate high-level language compiler into machine language), operating system (such as a batch system, time-sharing system, real-time systems ), service programs (such as diagnostics, debugger, linker, etc.), database management systems, networking software, and so on.
Applications: Also known as the application, it is the task requires the user according to various programs compiled, such as the scientific programs, data processing programs, process control procedures, transaction management procedures
Second, the hierarchical structure of the computer system
A computer problem solving process: high-level language programming is usually by the user (referred to as the source), and then it is fed with data within the computer, then the computer machine language program translated into machine-recognizable (referred to as target program), the machine automatically run a machine language program, and outputs the calculation result
Four level structure of a computer system:
✔ The third layer virtual machine (high-level language machine) translation by the compiler into assembly language programs or other intermediate language program
✔ The second layer of the virtual machine (assembly language machine) translation program in assembly language programs into machine
✔ a first layer of a conventional machine (machine-machine language) machine instructions interpreted by the microprogram
✔ zeroth layer microprogram machine (microinstruction system) directly executed by hardware microinstruction
Multi-level hierarchy of a computer system:
Virtual machine (high-level language machine) translation by the compiler into assembly language program
Virtual machine (assembly language machine) translation program in assembly language programs into machine
Virtual machine (OS machine) to explain the operating system in machine language
Conventional machines (machine-machine language) machine instructions interpreted by the microprogram
Microprogram machine (microinstruction system) directly executed by hardware microinstruction
Third, computer components and computer architecture
Computer Architecture: attribute refers to a computer system that can be seen programmer, i.e., the structure and functional properties conceptual
Computer system properties: generally refers to machine language programmer programming (including assembly language programmers and designers assembler) seen attributes of traditional machines, comprising a set of instructions, data type, memory addressing techniques, the I / O mechanism of, mostly belonging to the abstract properties.
Since the computer system having a multi-level hierarchy, therefore, stand attributes programmed computer programmer to see different levels are also different from each other.
Computer Organization: refers to how the results of the computer system embodied in the property, which contains many of the programmers is transparent to the hardware details.
When the two systems are the same machine instruction, only that they have the same structure. As to how the two functions of the machine to achieve its instructions, can differ, their compositions are different ways.
Computer Architecture and Computer Organization distinguish these two concepts are very important.
The basic composition of 1.2 computers
First, the characteristics of the von Neumann computer
Von Neumann machine features:
✔ computer by the arithmetic unit, a memory, a controller, input and output devices of five components
✔ to instructions and data stored in the memory of equal status, and can search the address.
✔ instructions and data are represented by a binary number
✔ instruction by the operation code and address code composed of operation code to indicate the nature of the operation, the address operand code which indicates a location in memory
✔ instruction sequence stored in the memory. Normally, instructions are executed sequentially, under certain conditions, may be changed, or the order of execution according to the condition set based on the calculation result
✔ machine operator at the center, the data transfer between the memory device and input and output is done by operator.
Second, a hardware block diagram of the computer
A typical von Neumann computer is operator-centric.
Modern computer is converted in the memory as a center.
Computer five members:
Intermediate results of arithmetic and logical operations used to perform arithmetic, and the operation is temporarily stored in a computing unit
The memory used to store data and programs
The controller is used to control, program and data input command, the processing operation, and the calculation result
The input device is used to convert information in the form of the familiar form of machine recognizable information, a common keyboard and a mouse.
Output devices may be a machine operation result into the familiar form of information, such as a printer output, monitor output and the like.
Central processing unit (Central Processing Unit, CPU): As the operator and controller very close contact in the logic circuit and the result, especially after LSI production process occurs, these two components are often integrated on the same chip, Thus, they are typically collectively referred to as a central processing unit
I / O device (Input / Output Equipment): the input and output devices simply referred to as I / O device
Modern computer that consists of three parts: CPU, I / O apparatus and main storage (Main Memory, MM)
主机：CPU与主存储器合起来又可称为主机
外部设备：I/O设备又可称为外部设备
CPU is the core component ALU and CU
ALU (Arithmetic Logic Unit, ALU): referred to as arithmetic and logic units, arithmetic logic operation to complete.
The control unit (Control Unit, CU): used to interpret instructions in the memory, and issuing commands to perform various operation instructions.
The computer automatically work is done in an orderly manner under the unified command of the controller
Third, the steps of the computer
To solve a practical problem with the computer typically includes two steps: a variety of preparation before the machine, the machine is running
1) all kinds of preparation before the machine
In front of the machine all the preparatory work can be summarized as follows: a mathematical model to determine the method of calculation and preparation of problem-solving
Mathematical model: There are many scientific and technological problems is difficult to directly use a physical model to simulate the changes of the object being studied, such as the Earth's atmospheric circulation and so on. However, a lot of experiments and analysis, can always find a series of changes of the reaction studied mathematical equations. Typically, such models are mathematical equations called Variation of objects.
Determines the computing method: Since the mathematical equations in the mathematical model is often very complex, it becomes wishing to add suitable computer, subtraction, multiplication and division arithmetic, the corresponding calculation must be determined
Problem solving program preparation: all the steps of the program is suitable for machine operation, the preparation of the operational step problem solving procedure is described by a one-machine instructions
2) Run the machine
He said before the machine runs first talk about a few parts
· A main memory (referred to as main memory or memory): includes a storage body, the various components and logic control circuit.
Bank: a plurality of memory cells of memory banks, each memory cell also contains a number of storage elements (or memory cell, memory elements), each memory storage element can be a binary code "0" or "1."
Visible, a storage unit may store a string of binary codes, said string of binary code into a memory word, string of binary digits which is referred to as memory word length.
Each memory cell needs to have an address number, address number of storage units called
By address access mode: The operating mode is the main memory according to the address number of the memory cells is achieved for the bit storage memory (write), taken (read). This embodiment is referred by access address access mode, i.e. by address access memory (abbreviated access memory).
To address accessed by the implementation, main memory must also configure two registers MAR and MDR.
MAR (Memory Address Register): a memory address register, an address for accessing the memory cell to be stored, the number of bits corresponding to the number of memory cells
MDR (Memory Data Register): a memory data register is used to store the code extracted from a cell bank or to prepare the code into a memory cell, which is the number of bits stored word length and the like.
· Operator: operator to include a minimum of three registers (internal modern computer is often provided with general-purpose register group), and an arithmetic logic unit (ALU).
Three registers are: ACC, MQ, X
ACC (Accumulator): Accumulator
MQ (Multiplier-Quotient Register): Take quotient register
X: operand registers
Addition operation:
[M] ->X
[ACC]+[X]->ACC
Subtraction operation:
[M]->X
[ACC]-[X]->ACC
Multiplication operation:
[M]->MQ
[ACC]->X
0->ACC
[X]*[MQ]->ACC//MQ
Division operation of the process:
[M]->X
[ACC]/[X]->[MQ]
The remainder R in the ACC
· Controller
: Controller is the nerve center of the computer, from which each member of the automatic command, work in harmony.
Commonly referred to as a complete operating instruction fetch, analyze and execute stages.
Fetch process (also referred to as the fetch stage): the memory controller first reads out the command to an instruction, referred to as a fetch process.
Analysis (also called the analysis phase): Controller To analyze this instruction, the instruction indicate what kind of operation to be completed, according to the addressing characteristics specified address of the operand, called the analysis process
Execution (also known as the implementation phase): perform an action based on the number of addresses where the operation and the operation code instructions, known as the implementation process.
Controller by the program counter (Program Counter, PC), instruction register (Instruction Register, IR) and a control unit (CU) composition.
PC: used to store the address of the current instruction to be executed, there is a direct path between it and the main memory of the MAR, and having an automatic function, to automatically form the next instruction address.
IR: used to store the current instruction, IR content from the main memory of MDR.
CU: instructions for analyzing the current required to complete the operation, and issue a variety of micro-operation command sequences to control all of the controlled object.
I / O
I / O subsystem including various I / O devices and their corresponding interfaces.
Each I / O device by I / O link interface with the host, it receives various commands issued by the control CU, and complete the operation
1.3 computer hardware major technical indicators
measure a computer's performance advantages and disadvantages based on a number of technical indicators comprehensive determination. Both contain various performance indicators of hardware, but also contains a variety of functions of the software.
First, the machine word
Machine word: one refers to the CPU can process data bits, usually related to the number of bits of the CPU registers.
The longer the word length, the larger the range of the number, the higher the accuracy.
Second, the storage capacity
Capacity of the memory should include primary and secondary storage capacity of the memory capacity. I.e., the storage capacity of the storage unit number * = word length stored
MAR digits reflect the storage unit
Third, computing speed
Computer processing speed depends on many factors, such as the frequency of the machine, what operation is performed, the speed of the main memory itself (fast speed main memory fetch, access soon) are all related.
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