1.2 Development and classification of operating systems
Knowledge Graph
1. Manual operation stage (no operating system at this stage)
Perforated paper tape is the input and output device of early computers. It converts programs and data into binary numbers: 1 with holes and 0 without holes, which are input into the computer through photoelectric scanning. Then when people run the program, they input the paper tape filled with small holes into the computer. All work on the computer requires user intervention, and the contradiction between man and machine is increasing, so new solutions must be found.
There are two outstanding shortcomings in the manual operation stage:
- The user monopolizes the entire machine, and the resource utilization is low, but other users will not occupy resources;
- The CPU is waiting for manual operation, and the CPU is not fully utilized.
2. Batch processing stage (the operating system begins to appear)
In order to solve the contradiction between man and machine and the contradiction between CPU and I/O equipment speed mismatch, a batch processing system appeared. According to the development routine, it can be divided into single-pass batch processing system and multi-pass batch processing system .
1. Single-channel batch processing system
The single-pass batch processing system processes jobs in batches, but there is always only one job in the memory.
The main features of the single-pass batch processing system are as follows:
- Automation : Under normal circumstances, jobs on the tape can be run automatically one by one without manual intervention;
- Sequentiality : The order in which the jobs on the tape are completed is the same as the order in which they enter the memory;
- Single pass : Only one job is running in the memory.
The problem faced by the single-pass batch processing system is that only one batch processing task is stored in the host memory. Whenever it sends an input/output request during operation, the high-speed CPU will enter the state of waiting for the low-speed I/O device.
2. Multi-pass batch processing system
Multiprogramming technology runs multiple programs into the memory at the same time and alternately runs on the CPU. These programs can share all the resources in the system.
When a program is suspended due to an I/O request, the CPU can immediately switch to running another program. It does not use a certain mechanism to improve the bottleneck problem in a certain aspect, but makes every component of the system enter the use state as much as possible. Although it takes a certain amount of time to switch tasks, the parallel work of various components between systems can be realized, which doubles the overall efficiency per unit time.
The multi-pass batch processing system has the following characteristics:
- Multi-channel : Simultaneously put multiple independent programs in the computer memory;
- Macroscopically parallel : all programs entering the memory are in a running state;
- Microscopically serial : Multiple programs in the memory take turns occupying the CPU and execute alternately.
The realization of multiprogramming technology needs to solve the following problems:
- How to allocate processors?
- How to allocate memory for multi-programs?
- How are I/O devices allocated?
- How to organize and store a large amount of programs and data?
Advantages and disadvantages of multi-pass batch processing system:
- advantage:
- High resource utilization;
- The system throughput is large.
- Disadvantages:
- Long user response time;
- No human-computer interaction is provided.
Three, time-sharing operating system
Time-sharing technology: divide the running time of the processor into very short time slices, and allocate the processor to each online job in turn according to the time slice; if a job has not been completed before the time slice allocated to him is used up , The job is temporarily suspended, waiting for the next round of calculation. The processor is now available to another job.
The time-sharing technology is adopted in the operating system to form a time-sharing system. The time-sharing operating system allows multiple users to share the same host at the same time through the terminal, and users can interact with the host at the same time without interfering with each other. Therefore, the most critical problem in implementing a time-sharing system is how to enable users to interact with their own homework.
The time-sharing operating system also supports multi-program design, but it is different from the multi-channel batch processing system. The time-sharing operating system allows human-computer interaction, while the multi-channel batch processing system does not allow human-computer interaction.
The time-sharing operating system has the following characteristics:
- Simultaneity : Simultaneity, also known as multipath, refers to allowing multiple end users to use a computer at the same time;
- Interactivity : The user can directly control the computer through the terminal using man-machine dialogue;
- Independence : Multiple users in the system can operate independently of each other without affecting each other;
- Timeliness : User requests can be responded to in a short time.
Four, real-time operating system
In order to be able to complete certain urgent tasks within a certain time limit without time slice queuing, a real-time operating system was born.
The time limit here is divided into two situations:
- Hard real-time system : an action must absolutely occur at a specified time (or a specified time range);
- Soft real-time system : the task can accept occasional violations of time regulations without causing any permanent damage.
The characteristics of real-time operating systems are mainly timeliness and reliability .
5. Network operating system and distributed computer system
The network operating system organically combines the computers in the computer network to form a whole, providing a unified, economical and effective method of using each computer, and realizing the mutual transmission of data between the computers. The main feature of a network operating system is the sharing of various resources in the network and the communication between computers .
A distributed computer system is a system that consists of multiple computers and meets the following conditions:
- Any two computers in the system exchange information through communication;
- Every computer in the system has the same status, and there is no distinction between master and slave;
- The resources on each computer are shared by all users;
- Any computer in the system can constitute a subsystem and can be reconfigured;
- Any work can be distributed on several computers and completed by them in parallel and collaboratively.
The operating system used to manage the distributed computer system is called the distributed computer system, and its essential difference from the network operating system is that the same task is coordinated and completed by several computers in the distributed operating system.
The main characteristics of distributed computer systems are distribution and parallelism .
Six, personal computer operating system
Personal computer systems are currently the most widely used systems, with common ones such as Windows, Linux, and Mac OS.
Reference material: Wangdao postgraduate entrance examination-operating system