Computer composition principle-Reading Notes (9) Operating System Support

An operating system is a system software that manages computer resources and provides services to users. as an interface between hardware and application software, the operating system plays a crucial role.

 

Computer systems can be divided into three parts: hardware, system software, and application software. Hardware is the material basis for all software operations.

 

The operating system is the most important system software and the system software for managing computer system resources and controlling program execution.

 

Main objectives of the operating system: to manage system resources, improve system efficiency, facilitate user use, enhance machine functions, and build an open environment

 

Core tasks of the Operating System: Managing Resources in the Computer System

 

Hardware resources managed by the operating system as the Resource Manager: processor management, memory management, and device management

 

Processor management: the processor is the most important hardware resource. The execution of all software and the implementation of system functions depend on the processor.

 

Storage management tasks undertaken by the operating system: storage allocation, storage sharing, storage protection, and storage expansion

 

Device management: the main task of device management is to schedule and manage various peripheral devices and coordinate the I/O requests made by users, improve the concurrency between operations on each I/O device and the operation of the processor, and improve the utilization of the processor and I/O device. Device management also provides device drivers for various devices to shield users from hardware usage details.

 

Operating system features:

Concurrency: to improve the system resource utilization, the multi-task system uses the Concurrency Technology to eliminate the mutual waiting between components in the computer system.

Sharing: multiple concurrent programs need to share hardware and information resources in the system.

Randomness: in Multi-program environments, randomness is obvious.

 

Processor Status Control: To support operating system privileges, the central processor needs to know whether the currently executed program is operating system code or common user program code. Therefore, the status flag is set in the processor.

 

Privileged commands: commands in the command system are divided into privileged commands and non-privileged commands in a multi-task environment to prevent user programs from executing machine commands related to resource management and thereby undermining the normal operating status of the system.

 

Program status word and program execution site: in order to record the current working status of the computer system, you need to set the program status word (psw) to control the execution of commands and store the system status related to the program.

 

The information stored in the Program Status Register generally includes the following types:

The instruction address currently being executed, which is provided by the program counter.

The status condition code indicates the status features of the command execution result.

The processor status indicates the current processor status.

The control flag can affect some flag spaces of certain command execution methods.

 

Interruption mechanism:

Modern computer systems support interruptions (exceptions ). By detecting the interrupt source and responding to the interrupt, the interrupt mechanism provides a method for random program switching.

A software or hardware fault may occur randomly when the computer is working, and the time is completely random relative to the CPU command execution. In the event of a fault, the CPU should execute the Interrupt Processing Program for processing.

 

Storage Management: the system hardware supports the operating system to implement a multi-level storage system and storage protection functions through the storage management components.

 

A program is a static object.

A process is a dynamic entity and a program in execution. A process not only contains program code, but also the current status and resources.

 

Process status: Process Creation, ready process, running process, blocking process, Process Termination

 

Multiple processes can be created, ready, blocked, and terminated, but the processor can only run one process at any time.

 

Process control block (PCB): to manage and control processes, the operating system must store information about the status of each process. Therefore, the operating system sets a PCB for each process. The PCB records all information required by the operating system to describe the process and control the process operation.

 

Implementation of Processor Scheduling: For the convenience of scheduling, the operating system will establish and maintain several process queues. Each queue is used to maintain a list of processes waiting for certain resources.

 

Exchange Technology: it consists of two processes: Exchange and exchange. During the SWAp process, the data and program code in the SWAp area are switched to the memory, and vice versa.

Paging technology: Virtual Memory (virtual storage)

 

The replacement of cache depends on hardware, and the replacement of virtual memory is supported by the operating system.

Computer composition principle-Reading Notes (9) Operating System Support