The basic composition and working principle of computer

The basic composition and working principle of computer

1.3.1 the composition of the computer system

Computer system is composed of hardware and software system, this section will introduce computer hardware system and software system respectively.

Computer Hardware is a collection of functional parts of a computer system. is composed of electronic, mechanical and optoelectronic components of various computer components and equipment, is the computer to complete the work of the material base. Computer hardware is a physical entity that is visible, tangible, and physically present.

Computer software refers to a variety of programs related to the operation of a computer system, as well as any related documents and data collection. The program is a sequence of statement instructions for computer execution that is described in the programming language.

Computers that do not have any software installed are often referred to as "bare metal" and bare metal does not work. If the computer hardware is out of the computer software, it becomes a useless machine. If the computer software is out of the computer's hardware, it loses the material base of its operation, so the two interdependent, indispensable, together constitute a complete computer system.

The basic composition of the computer system is shown in 1-6.

Figure 1-6 Basic components of a computer system

1.3.2 the basic composition and working principle of computer hardware system

Modern computer is an automatic information processing device, it can realize automatic information processing, is due to the use of "memory program" work principle. This principle was 1946 by von · Neumann and his colleagues were presented and argued in a paper entitled "Preliminary discussion on the design of electronic computer logic". This principle establishes the basic composition and working mode of modern computer.

The ⑴ computer hardware consists of five basic components: an operator, a controller, a memory, an input device, and an output device.

The ⑵ computer internally uses binary to represent programs and data.

⑶ uses "stored program" method, the program and data into the same memory (internal memory), the computer can be automatically high-speed out of the memory instructions to execute.

It can be said that each of the five parts of the computer hardware has a relatively independent function, respectively, to complete their respective work. As shown in 1-7, the five components are actually working in a coordinated and unified manner under the control of the controller. First, the program that represents the calculation step and the original data needed in the calculation, under the control of the controller input command, are fed into the computer's memory storage by the input device. Secondly, when the calculation begins, the program instruction is fed into the controller by the function of taking instruction. The controller decodes the instruction and, according to the operation requirements of the instruction, sends the storage, the number of commands and the arithmetic commands to the memory and the arithmetic, which is calculated by the operator and stored in the memory. The output of the output device is calculated based on the controller's fetch and output commands.

1 . Arithmetic device (ALU)

An operator is also known as the Arithmetic logic unit alu (arithmetic logic units). Its function is to complete arithmetic and logical operations. Arithmetic operations refer to addition, subtraction, multiplication, addition and their complex operations. Logical operation refers to the operation of logical comparison and logical judgment, such as "and", "or" and "non". In a computer, any complex operation is transformed into a basic arithmetic and logical operation, which is then done in an operator.

2 . Controller (CU)

Controller CU is the command system of the computer, and the controller is usually composed of instruction register, instruction decoder, sequential circuit and control circuit. Its basic function is to access instructions and execute instructions from within. An instruction is a step that instructs the computer how to work, consisting of the opcode (Operation method) and the operand (operand). The controller accesses the memory through the address, extracts the selected unit instruction, analyzes the instruction, and uses the control signal produced by the instruction for the other parts to fulfill the instruction requirement. This cycle of work ensures that the computer can work automatically and continuously.

It is commonly referred to as the Central processor , the CPU (the central processing Unit), which is the core part of the whole computer and the "brain" of the computer. It controls the operation, processing, input, and output of the computer.

Integrated circuit technology is the basic technology to manufacture the CPU of microcomputer, small machine, mainframe and giant machine. Its development has greatly improved the speed and ability of the computer. In 1965, the founder of chip giant Intel Corporation Gordon · Moore, gives the famous Moore's law: The number of transistors on a chip doubles every 18-24 months. To everyone's surprise, the law is a very accurate predictor of the 30-year development of the chip. The 1958 first-generation integrated circuit contained only two transistors, whereas in 1997, the Pentium II processor contained 7.5 million transistors, and the 2000 Pentium 4 had reached 0.13 micron Technology, integrating 42 million transistors. The larger the number of transistors integrated into the CPU, the more powerful the chip computing power.

3. Storage (memory)

Memory is a computer memory device, its main function is to store programs and data. The program is the basis of computer operation, the data is the object of computer operation.

⑴ Information Storage Unit

Programs and data are stored in memory in binary form on the computer. The size of the storage capacity is measured in bytes. It is often expressed in kilobytes (kilobytes), megabytes (MBytes), GB (gigabytes), and terabytes. The relationship between them is: 1kb=1024b=210b,1mb=1024kb=220b,1gb=1024mb=230b,1tb=1024g=240b, in some calculations in order to calculate the simplicity of the 210 (1024) is often assumed to be 1000.

bit (bit): is the smallest unit of data stored by the computer. A single symbol "0" or "1" in a machine word is called a bits, which can hold a binary number.

Byte (byte, abbreviation B): bytes are the unit of measure of the computer's storage capacity and the basic unit of data processing, and 8 bits constitute a byte. A single byte of storage space is called a storage unit.

Word: When a computer processes data, the length of data that is accessed, processed, and passed is called a word. A word is usually made up of several bytes.

Word Long: The length of the data that the central processor can process at the same time is long. The length of the CPU determines the data width of the register and bus. The word length of modern computers is 8-bit, 16-bit, 32-bit, 64-bit.

Classification of ⑵ Memory

The degree of memory-to-CPU connection is divided into two categories: internal memory (main memory) and external memory (secondary memory). Memory in the computer host, it directly with the operator, the controller exchange information, the capacity is small, but the access speed is fast, usually only store those running programs and data to be processed. In order to enlarge the capacity of internal memory, the introduction of external memory, external memory as an extension and backup of internal memory, indirect and CPU connection, used to store some systems must be used, but do not rush to use the program and data, the program must be transferred into the memory to execute. External memory access speed is slow, but the storage capacity is large, can save a lot of information for a long time. The relationship between the CPU and the internal and external memory is shown in 1-8.

Semiconductor memory is widely used in modern computer systems, and from a functional point of view, semiconductor memory can be divided into two categories: volatile (volatile) memory after power loss and non-volatile (non-volatile) memory that does not lose data after power loss. Ram in a microcomputer belongs to a random read-write volatile memory, and ROM is non-volatile (non-volatile) memory

How ⑶ Memory Works

To better store programs and data, memory is often divided into many equal-length storage units, each of which can hold information in a suitable unit. All storage units are numbered in a certain order, which is referred to as the address of the storage unit, referred to as the address. The relationship of the storage unit to the address is one by one corresponding. It should be noted that the address of the storage unit and what is stored inside it are completely different.

The operation of memory is often referred to as access memory, there are two methods of accessing memory, one is to save data to the storage unit after the selected address, which is called "write", and the other is to extract the data from the selected storage unit, which is called "read". It can be seen that the address of the storage unit must be given first, whether it is read or write. The memory address from the address bus is decoded (converted) by the address decoder, the corresponding memory unit is found, and the read/write control circuit determines the access mode of the memory according to the corresponding read and write commands, and completes the read and write operation. The data bus is used to transmit information that is written to memory or removed from memory. The main memory structure is shown in block Diagram 1-8.

4. input Device

An input device is a device that transmits information from outside the computer to the inside of a computer. Its function is to convert data, programs, and other information from familiar forms to computers that can be identified and processed in a form that is entered into the computer.

The commonly used input devices are keyboard, mouse, stylus, scanner, digitizer, barcode reader and so on.

5. Output Device

An output device is a device that transmits the results of a computer's processing to an external computer for use by a computer user. Its function is to convert the data information in the binary form of the computer into the form of information that people need or other devices can accept and recognize. Common output devices are display, printer, plotter and so on.

Typically we refer to input devices and output devices collectively as I/O devices (input/output). They all belong to the computer's external devices.

1.3.3 Computer software system

a complete computer system is composed of two parts: hardware and software. Hardware is the physical entity that makes up a computer. But only the hardware computer can not work, to make the computer solve various problems, must have software support, software is between the user and hardware system interface.

The word "Software" was introduced into China in the early 1960s. The International Organization for Standardization (ISO) defines software as: The general name of the procedures, rules and documents necessary for the computer program and the application of the data processing system. An accepted explanation for this definition is that the software consists of two parts: the program and the document. The program is composed of the most basic instructions of the computer, is the computer can recognize and carry out the operation steps, the document is written in natural language or formal language to describe the program's content, composition, functional specifications, development, test structure and use of text materials and charts. The program is purposeful and enforceable, and the document is the interpretation and description of the program.

The program is the main body of the software. The software can be divided into two types: System software and application software according to its function.

1. 1. Systems Software (System software)

System software generally refers to the control and coordination of computer and external equipment, supporting the application software development and operation of the system, is a collection of programs without user intervention, the main function is to dispatch, monitor and maintain computer systems, responsible for the management of computer systems of various independent hardware, so that they can coordinate work. System software allows computer users and other software to treat computers as a whole without having to take into account how each of the underlying hardware works.

Common system software mainly refers to the operating system, of course, including language processing programs (assembly and compilation programs, etc.), service programs (support software) and database management system.

⑴ OS OS (Operating system)

The operating system is the core of the system software. In order for all the resources of a computer system, including hardware and software, to work in a consistent and methodical manner, one software must be used for unified management and unified scheduling, which is called the operating system. Its function is to manage the computer system of all hardware resources, software resources and data resources, as shown in Figure 1-10, the operating system is the most basic system software, all the other software is built on the basis of the operating system. Operating system is the interface between the user and the computer hardware, no operating system as a mediator, the user's operation and use of the computer will become very difficult and inefficient. The operating system can reasonably organize the whole work flow of the computer and maximize the utilization of resources. Operating system provides users with a convenient, friendly, flexible service interface, but also provides other software development, running platform. It has five functions, namely CPU management, job management, memory management, equipment management and file management. The operating system is an essential piece of software for every computer, and now has a certain scale of modern computers and even a few different operating systems. The performance of the operating system largely determines the merits and demerits of computer system work. Microcomputers commonly used operating systems are DOS (Disk Operating system), Unix, Xenix, Linux, windows98/2000, NetWare, WindowsNT, WindowsXP and so on.

⑵ Language Processing Program

Before introducing the language processing program, it is necessary to introduce the development of computer programming language first.

Software refers to the various programs in a computer system, and a program is a sequence of instructions that is described in the language of computers. Computer language is a tool of communication between man and computer, and this kind of communication is called computer programming. The programming language can be divided into three kinds according to its developing process: machine language, assembly language and high-level languages, the former are collectively referred to as low-level languages.

Machine Language is directly made up of machine instructions (binary), so the computer program written by it does not need translation to be directly recognized and run by the computer system. The greatest advantage of this program, written by binary code directives, is its fast execution, high efficiency, and serious shortcomings: machine language is difficult to master, programming cumbersome, poor readability, error-prone, and dependent on the specific machine, poor versatility.

Assembly language (Assemble Language) uses a mnemonic notation to denote instructions and data in a machine language, a symbolic machine language, also known as a "symbolic language." Assembly Language Program instruction operation code and the operation number are all with the symbol expression, greatly facilitates the memory, but uses the mnemonic symbol to represent the assembly language, it and the machine language is in the final analysis is one by one correspondence relation, all relies on the concrete computer, therefore all is the low-level language. Also have the shortcomings of machine language, such as: lack of versatility, cumbersome, error-prone, and so on, but the extent of the difference. A program written in this language (assembler) cannot be run directly on a computer, and must first be "translated" into a machine language program by a system program called a assembler before it can be executed by a computer. Any computer is equipped with a assembler program (assembler) that is applicable only to itself.

The high-level language, also known as the Algorithmic language, is machine-independent and is a computer language similar to human natural language or mathematical formulae. High-level language overcomes the many shortcomings of low-level language, it is easy to learn, easy to use, readable, expressive ability (the statement is more similar to the natural language of the English word to express), good versatility (in high-level language programs can be used on different computer systems). However, programs written for high-level languages still cannot be recognized and executed directly by the computer, and it must undergo some kind of conversion to execute.

There are many high-level languages, high-function, commonly used advanced languages are: process-oriented basic, FORTRAN for scientific computing, Pascal supporting structured programming, COBOL for business processing and C language for modern software development And now there is an object-oriented VB (Visual Basic), VC + + (Visual C + +), Delphi, Java and other languages so that the ability of computer language to solve practical problems has been greatly improved.

The Øøfortran language was introduced in 1954 and was realized in 1956. It is suitable for scientific and engineering calculation, it already has quite perfect engineering design Calculation Program library and engineering application software.

Øøpascal language is a structured programming language, suitable for teaching, scientific computing, data processing and system software development, and is gradually replaced by C language.

The Øøc language is a successful development of the Bell Laboratory in the United States and a high-level language with great flexibility. Its language program is concise, powerful, suitable for system software, data calculation, processing, etc., become one of the most used programming languages.

Øøvisual Basic is an object-oriented programming language developed on the basis of basic language, which preserves the simple and easy-to-learn characteristics of basic language, and has a strong visual interface design function, which can develop Windows application quickly. is an important language for multimedia programming tools.

Øøc++ is an object-oriented language. Object-oriented technology has been widely used in many fields such as System program design, database and multimedia application. Experts predict that the object-oriented programming concept will lead to the development of programming language in the future.

Øøjava is a new type of cross-platform distributed and programming language. Java is a world wide concern for its simplicity, security, portability, object-oriented, multithreading, and dynamic features. The Java language is based on C + +, and its greatest feature is "write once, run everywhere". Java has gradually become the core language of networked software.

The function of a language processor is to translate programs written in other computer languages, in addition to machine language, into a machine language program that can be directly identified and executed by the machine. Can be divided into three types, namely assembler, compiler and interpreter. A computer program written in assembly language and various high-level languages is usually called the source program, and the machine instruction program generated by the source program (compiled or compiled) is called the object program. The assembler in the language processing program and the compiler have a common feature, that is, the target program must be generated, and then get the final result by executing the target program. And the interpreter is to interpret the source program (sentence by step translation), the translation of an execution sentence, side interpretation side execution, thus obtaining the final result. The interpreter does not produce the target program that will be executed, but instead uses the interpreter to directly execute the source program itself.

It should be noted that, in addition to machine language, each computer language should have a corresponding language processing program.

⑶ Service Program (support software) refers to a class of programs designed to help users to use and maintain computers, provide service means, and support other software development. The contents of such programs are extensive, mainly in the following categories:

Øø Tool Software: Tool software is primarily software tools that help users to use computers and develop software, such as the PC tools that are launched by US central Point software company.

Øø Editing Program: The editing program can provide a good writing environment for users. such as Edlin, EDIT, writing board and so on.

Øø Debugger: The debugger is used to check what errors the computer program has, as well as the error location, in order to fix it, such as Debug.

Øø Diagnostics: The diagnostic program is mainly used to detect and maintain the hardware of the computer system. Can detect the performance and fault of CPU, memory, hard drive, monitor, keyboard and I/O interface.

⑷ database management System.

Database technology is one of the fastest growing and widely used branches in computer science, which can be said to be inseparable from database technology in the future of computer application development. The database management system is a large-scale system software that organizes, manages and queries the large amount of data stored in the computer to provide certain processing function effectively. Mainly divided into two categories, one is based on micro-computer database management system, such as Foxbase and FoxPro, the other is a large database management system.

2. 2. application software

Application software is a program that is developed to solve various practical problems in various fields of computer application, which is used to help people to complete various work in specific fields. Application software mainly includes: to solve a variety of practical problems of the program, it is used to help the rib people to complete a specific field of work. Application software mainly includes:

⑴ Word Processor: A word processing program used for text input, editing, typesetting, printing and output programs, such as Microsoft Word, Wps2000, and so on.

⑵ form processing software: A spreadsheet processor program used to computer, process, and print out spreadsheets, such as Lotus, Excel, and so on.

⑶ aided design software: A software development program is a program or package that is provided for the user to design a variety of applications. AutoCAD, Photoshop, 3D Studio max, etc. are commonly used. In addition, the various language and language processing procedures described above also provide users with tools for application design and can also be considered as software development programs.

⑷ Real-time control software: In modern factories, computers are commonly used for automatic control of production processes, called "real-time controls". For example, in a chemical plant, the use of computer control ingredients, temperature, valve opening and closing, in the steel-making workshop, with computer control feeding, furnace temperature, smelting time, etc. in power plants, with computer control generator sets. This kind of control to the computer reliability requirements are very high, otherwise will produce unqualified products, or cause a major accident. At present, the more popular software on PC is fix, InTouch, Lookout and so on.

⑸ user Application; A user application is a program designed by a user to use the various languages and software development programs described above for a specific task. such as personnel file management procedures, computer-aided teaching software, a variety of game programs.

The basic composition and working principle of computer