Shulou(Shulou.com)06/03 Report--

Von Neumann architecture: (a computer must have four parts: input and output, memory, processor)

Input device-> memory-> output device

| (two-way Arrow)

Arithmetic unit

Controller (used to control input, output, memory, arithmetic unit)

The processor includes arithmetic unit and controller.

Note: 1) the memory here refers to memory. 2) CPU can only access memory, not peripherals. 3) peripherals can only be written to or read from memory

two。 Operating system: software for "management"

Managers have two kinds of tasks: hardware management and software management.

According to the target object, it can be divided into two types: internal management and external business management.

3. Process: for the operating system, a task is a process

4. Time slice: today's operating systems all support multitasking, and the task scheduling of the operating system adopts the preemptive scheduling mode of time slice rotation (one task is forced to pause to execute the next task after a short period of time).

A short period of time during which a task is executed is called a time slice, and the state when the task is being executed is called the running state.

A CPU performs time slice rotation and task scheduling within a period of time.

5. Concurrency and parallelism:

Concurrency: multiple processes use time slice rotation under one CPU, which enables multiple processes to advance within a period of time, which is called concurrency (single processor multi-process).

Parallel: multiple processes run simultaneously under multiple CPU (multiprocessor and multiprocess)

6. Kernel mode and user mode:

The operating system grades the execution permissions: user mode and kernel mode

Kernel mode: the operating system kernel, as the underlying software that directly controls the hardware device, has the highest authority.

User mode: the user program has the lowest permissions

7. Context in the process: context is simply an environment

Context: when a process executes, the values in all registers of the CPU, the state of the process, and the contents on the stack

When switching, you need to save all the states of the current process and the process environment of the current process, so that when the process is executed again, the state of the switch can be restored and execution can continue.

8. Process status: create, ready, run, terminate, block

State transition:

The process in the ready state becomes running after getting the time slice

The process time slice of the running state becomes ready after being used up.

A process in running state becomes blocked after an event occurs (such as waiting for an Ithumb O request)

A process in the blocking state becomes ready after completing an event, such as the completion of an Iripple O request

Ready: the process is runnable, but the CPU time slice has not been rotated to the process

Run: the process is runnable and the CPU timesheet goes to the process, which is executing code

Blocking: the process does not have the conditions to run and is waiting for an event to complete

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