Definition
Terminal refers to the place where information can enter or leave the communication network. It sends information to the network and can also receive information from the network. The characteristic of the terminal is that the computer in the computer network can be used remotely through terminal equipment (such as a teletypewriter, a display device with a keyboard, etc.), and the computer can also be used after dialing through a dedicated telephone number.
Terminals can be divided into batch processing terminals and interactive terminals according to their working methods.
Interactive terminal is a kind of terminal used to exchange information between man and machine. Its working method is relatively simple, it only has the function of inputting information and outputting information, it cannot complete any information processing actions by itself, and it cannot modify, explain, or change the data information from all parties. Receiving or sending can only be activated by pressing a key or a message sent from the central host computer. It works slowly, and is generally composed of a teletypewriter or keyboard display device plus a modem.
Classification basis
Output performance
In terms of their output performance, interactive terminals can generally be divided into print output and video display devices.
The print output terminal is sometimes called a teletypewriter or teletype machine. It is a recording paper output like a typewriter, usually using punching technology or dot-matrix printing technology. Later, non-impact printers appeared. Some manufacturers provided hot-spot devices that used photosensitive paper that could change color when heated in the printing area. The character string is printed by selectively heating the guide pin in contact with the paper, which has a unique feature of no noise. What needs to be pointed out is that laser-based electrostatic printing, ion precipitation printing and ink jet printing have been successfully applied to output peripherals and have broad development prospects.
Video display terminals have been more widely used. Usually, video display devices use oscilloscope tubes for scanning output. Display terminals are a kind of "soft copy" output devices, and they are not left on the table. Download any tangible files, and in the application, they can be connected with an auxiliary printer, and can also provide a larger or smaller screen size than this. Although graphics display performance is becoming more and more important, most video display terminals are still alphanumeric devices, which support character sets of 96-256 different symbols. Most are dot matrix devices. Each character is formed in a predetermined pattern by the bright spots on the screen. This kind of terminal is generally equipped with a character generation table stored in a read-only memory. Once the input character code is received, the terminal microprocessor will call the corresponding dot matrix model to be displayed.
The way the equipment is structured
From the composition of the interactive terminal equipment, there are three structures. The most common one is the keyboard sending and receiving (KSR) terminal. It can both send data and receive data. It is characterized by a keyboard that can be used to input data or type commands. The output device can be a printer or a display screen. The keyboard itself is connected to the terminal base or connected to the terminal through a flexible wire. There are several keyboard specifications, the most popular is the combination of IBMSelecticTM typewriter and a keyboard, which can start and control data transmission. ·
The second type of terminal structure is called Receiver Only (RO), which can display and print data from the computer, but it cannot send data by itself. The difference between Receiver Only and Keyboard Transmitter and Receiver is Is there a keyboard. Receiver-only display terminals are widely used for information transmission in airports, restaurants and other public facilities. When selecting paper output, only the typewriter must be connected to the keyboard sending and receiving display terminal.
The third terminal structure is the automatic sending/receiving device (ASR), which is still used in many older models. It is composed of KSK terminals and peripheral accessories or internal Electronic memory composition. Before establishing a connection with the computer, use it to prepare machine-readable information or other data. In the past, ASR used a tape reader/puncher to continuously transmit pre-recorded information or other data on paper tape or polyester tape instead of keyboard entry. This type of terminal was widely used for reporting services in the 1970s. This offline data preparation before transmission can significantly shorten the processing time and the resulting long-distance call charges. In the early 1980s, most of the automatic sending/receiving devices ASR terminals have been updated to tape recorders/readers or floppy disk drives.
Types and complexity of electronic circuits
From the perspective of the electronic circuits and information processing capabilities of the terminal, interactive terminals are usually divided into three types: simple terminals, flexible terminals and smart terminals Type.
Simple terminal is the oldest and simplest of the three. They are called so because they do not have the ability to process information.
Although the flexible terminal does not have enough information processing capabilities, it already has some of the main features of a microprocessor. The staff can choose different display performance, transmission rate and printing performance on the terminal. When neither the simple terminal nor the flexible terminal can meet the needs of the user, the smart terminal can be selected. It is actually a dedicated microprocessor composed of certain hardware and software. The user can use the smart terminal before sending and receiving data to other terminals or computers. Prepare the data and do some modification, editing and other preprocessing work.
Smart interactive terminal
Smart interactive terminal (smart interactive terminal) is abbreviated as smart terminal. Central processing unit. Compared with the traditional central processing unit, the microprocessor has the advantages of small size, light weight and easy modularization. Its basic components are: register file, arithmetic unit, timing control circuit, data and address bus As the operation control component of a microcomputer, it can be combined with memory, peripheral circuit chips, etc. to form a type of interactive terminal of a microcomputer. This type of terminal can perform certain tasks before sending information to the computer or after receiving data from the computer. Processing, which can greatly reduce the workload of the computer.
Intelligent interactive terminals have the functions of input and output, storage and processing of information. Intelligent interactive terminals generally include keyboards, displays, printers, microprocessors, memory, and input/output interfaces. Other external devices such as floppy disks can be connected.
Application
Interactive terminal retrieval
There are generally two types of user retrieval of real-time database: program call and interactive terminal search, program call It is a method of using one or several programming languages to compile subroutines or functions for users to implement data retrieval from the database through the main program reference. This method is mostly used in routine, relatively fixed, automated business systems. The main parameters in the subroutine or function should include: data type, date/time, data range, data level, element name, output format, etc.
The interactive terminal retrieval function is more flexible than the program call. In addition to all the functions of the program call, it can also have the statistical function of the data, and it can even realize the visual display of the data.
Interactive information publishing system
The interactive information publishing system includes an interactive terminal and a server communicating with the interactive terminal.
The interactive terminal includes a shell, the shell is provided with a touch screen, a control motherboard and a processor are arranged in the shell, and the control motherboard is electrically connected to the processor; the control motherboard is provided with communication Device; an interactive terminal communication device to communicate with the server; an audio device connected to the control motherboard is provided on the housing. The interactive terminal in the interactive information publishing system is equipped with a touch screen, which can conveniently input, update and display information, which is conducive to improving the timeliness of the message, and is conducive to the user to obtain the information of interest in time; The recognition module and the WIFI module allow the operator to release information on site and confirm the release effect in time, which also improves the speed of information update.