"Operating System-Essence and Design Principles" Study Notes Chapter 2
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"Operating System-Essence and Design Principles" Study Notes Chapter 1
"Operating System-Essence and Design Principles" Study Notes Chapter 2
2.1 Objectives and functions of the operating system
The operating system is the program that controls the application program and the interface between the application program and computer hardware. It has three main goals:
- Convenience: the operating system is easier to use for the computer
- Effective: The operating system allows a more efficient way to use computer system resources
- Expansion capability: when constructing the operating system, it should be allowed to effectively develop, test and introduce new system functions without hindering the service
2.1.1 Operating system as user/computer interface
Simply put, the operating system provides a series of interfaces for some functions that programmers need to use when developing applications; it acts as an intermediary, allowing programmers and applications to more easily access and use the following functions and services.
- Program development
- Program running
- I/O device access
- File access control
- System access
- Error detection and response
- Bookkeeping
- Command System Architecture (ISA)
- Application Binary Interface (ABI)
- Application Programming Interface (API)
2.1.2 Operating system as a resource manager
A computer is a group of resources and controls these resources, and the operating system is responsible for managing these resources.
From a certain point of view, the operating system is controlling the movement, storage and processing of data, but this control is implemented in an unusual way. The difference from the traditional control mechanism is reflected in the following two points:
- The operating system has the same function as ordinary computer software, that is, it is also a section or group of programs executed by the processor
- The operating system often releases control and must rely on the processor to restore control
2.1.3 Easy scalability of operating system
The operating system should be able to evolve continuously for the following reasons:
- Hardware upgrades and the emergence of new types of hardware
- New service
- Correct the error
2.2 The history of the operating system
Understanding the development history of operating systems will not only help understand the key design requirements of operating systems, but also help understand the meaning of the basic features of modern operating systems.
2.2.1 Serial processing
Early computers used serial processing, but this processing method has the following two disadvantages:
- Scheduling problem: Most devices will schedule the time of the machine. If a program is scheduled for an hour but completes the work in 45 minutes, the remaining time will be wasted; if the work is not completed within the scheduled time, it will be forced stop.
- Preparation time: The preparation time before the program runs is very long. If there is an error in the preparation process, the preparation needs to be restarted.
2.2.2 Simple batch processing system
In order to improve utilization, people began to develop batch processing systems, the central idea of which is to use a software called a monitoring program. By using this operating system, users can hand over jobs in cards or tapes to a computer operator, who organizes the jobs into batches in sequence, and puts the entire batch of jobs on the input device for use by the monitoring program. After each program is processed, it returns to the monitoring program, and the monitoring program automatically loads the next program.