1, manual operation - punchcards - tape
Manual mode two characteristics:
(1) user exclusive whole machine. The phenomenon does not occur because resources have been occupied by other users and wait, but the low utilization rate of resources.
(2) CPU waits for manual operation. CPU utilization is not sufficient.
The late 1950s, the emergence of
human contradiction
: the formation of a sharp contradiction between the slow speed of manual operation and high speed computers, the manual mode of operation has seriously damaged the utilization of system resources (the resource utilization dropped percent a few, or even lower), can not be tolerated. The only solution: get rid of people only manual operation, automatic transition job. This appeared to
batch
.
2, Batch - tape storage
Online Batch:
First there is an online batch systems, input / output operations by the CPU that is processed
Offline batch processing system:
To overcome with ease: the contradiction slow-speed host and peripherals, improve the utilization of the CPU, and the introduction of off-line batch processing system , the input / output from the host control.
Tape storage reduces the time input / output, improved cpu utilization
3, multi-channel operating system appears
The so-called multi-channel programming technology, refers to allow multiple programs at the same time and run into the memory. I.e., while the plurality of programs into memory, and allowing them alternately run in the CPU, they share a variety of hardware and software resources in the system. When a program due to the I / O request to suspend operation, CPU will immediately turn to run another road program.
Can appear multiple tasks on a single computer at the same time, improve the cpu utilization;
Be able to use the resources of multiple tasks isolation, when a task encounters an input-output operation, allowing another task using the cpu to calculate, simply switch will be a waste of time
What is the I / O?
Input: input
Like Memory Access: read / recv / import / input
Output: output
Like memory Output: write / send / print
4, sharing operating system - round-robin
Since the CPU speed and the continuous improvement of time-sharing techniques, a computer can be connected to a plurality of user terminals, and each user can use the computer on-line own terminal, if their machines as exclusive.
Timesharing: operating the processor time is divided into short time pieces alternately allocated to each time-slice processor online job.
If a job can not be completed within the calculated time slice allocated to it, the job is temporarily interrupted, the processor used to give another job, and then continue its operation while waiting for one. Because the computer is fast, very fast rotation job runs, giving each user the impression that if he monopolized a computer. And each user can issue various commands to the system through the operation control his own terminal, in the case of fully interactive, run the job is completed.
The computer system having the above characteristics is called time-sharing system, which allows multiple users to use the online computer.
Features:
(1) Multiple sex. A plurality of users simultaneously use a single computer. Each user in turn is microscopically using a computer; macroscopically in parallel to each user.
(2) interaction. The user may further proposed a new request to the system according to the results of the system in response to the request. This enables users with a system of man-machine dialogue mode of operation, significantly different from the batch system, therefore, time-sharing system is also known as interactive systems.
(3) independence. The user can operate independently of each other, without disturbing each other. Systems to ensure the integrity of each user program is running, confused with each other or destruction does not occur.
(4) Timeliness. The system can promptly respond to user input. One of the main indicators of the performance of time-sharing system response time, which means: to issue commands to the system to be the time required for the response from the terminal.
The main objective of the time-sharing system
: in response to a timely user, i.e. the user will not wait for the processing time of each command is too long.
Simultaneously sharing system may receive dozens or even hundreds of users, due to limited memory, storage method often used to change (also known as switching) mode. Not about to "turn" the work into the disk, once the "turn", and then it transferred to the memory; and the time sheet after use, turn the job saved to disk (commonly known as "roll forward", "Get out" law ), the same storage area in turn serve multiple users.
Multi-user time-sharing system is a kind of operating system of today's computer operating system is the most commonly used.
Note: The time-division time slice operation of the system, at the time did not encounter IO operations to run out their time sheets are cut away so that the switch did not actually work to improve the efficiency of the cpu, but makes reducing the efficiency of the computer . But we have to sacrifice a little efficiency, but to achieve the effect of multiple programs implemented jointly, so you can listen to music on the computer while talking qq.
5, real-time operating systems - real-time response to user commands
Although the multi-batch system and a time-sharing system to get a more satisfactory resource utilization and system response time, but it can not meet the needs of real-time control and real-time information processing two applications. Thus a real-time system, i.e. the system able to respond to randomly occurring external events, and the event processing is completed within a strict time.
Real-time system in a particular application often used as a control device.
Real-time systems can be divided into two categories:
(1) real-time control system. When the automatic flight control for an aircraft, missile or the like, requires a computer system can process the measurement data measured quickly and timely control of the aircraft or missile, or the relevant information to the decision-makers via the display terminal. When used in rolling, petrochemical industrial process control, the computer can also require timely processing of the data sent from various sensors, and controls the respective actuators.
(2) real-time information processing system. When used to book airline tickets, asking about flights, routes, fares, etc., or when used in the banking system, information retrieval systems, require the computer to be timely and correct answer can request sent by the terminal equipment services. Such requirements of timely response weaker in the first category.
Real-time operating system, the main features
:
(1) a timely response. Each information reception, processing and transmission of process analysis must be completed within a strict time limit.
(2) high reliability. Redundancy measures to be taken, before and after the two-stage system work, as well as the necessary security measures.
Sharing - now popular PC, server are using this mode of operation, i.e. the operation of the CPU time slice is divided into several different computing process each request linux system
in real time - typically a microcontroller, PLC, etc., such as the elevator down control, the operation keys and the like for the real-time processing requirements
Time-sharing system and compare real-time systems