Python second lesson (operating system introduction)

1. Why do I need an operating system

Starting from the definition of the operating system, the operating system is the control program that coordinates, manages and controls the computer hardware resources and software resources. Which is the middleman who takes our software applications and hardware calls.

The operating system is located between the computer hardware and the application software, is essentially a software, but maybe he will have millions of lines of code, today we have no effort to study him. Accurately speaking, the operating system is divided into kernel departments and system calls two parts, the operating system sometimes with software interaction, sometimes called hardware to work, so we simply say the operating system is always in the kernel state is not correct.

So what do the kernel states and system calls do for programmers, and we analyze them a little bit:

The 1 kernel feature hides the various hardware calling interfaces in the underlying board, providing programmers with a simpler and clearer system invocation interface, where we no longer have to consider the underlying hardware interface, because the operating system will help us get everything done.

2 Many of the software we install will share a set of resources for our computers, but when the program is competing, our hardware is not self-judging, which is the operating system will set a certain resource allocation rules for hardware, so that disorderly competition becomes orderly.

2. Location of the operating system

The operating system is a set of large-scale system software between the underlying hardware and the application software, and he can transform the instruction of the application software into the machine code that can be recognized by the hardware, thus realizing the interaction and communication between hardware and software.

3. Functions of the operating system

Through the kernel function shielding the underlying circuit structure and hardware interface, and then through the system calls to achieve soft and hard interoperability.

4. Development of the operating system

Generally speaking, the operating system has gone through the process of nothing, why should I say so? Because our first generation computer is no operating system, only the body has no soul, the word thin, I really do not define such an operating system, so alone to get out to make a statement out.

The first generation operating system was actually born after the second generation of computers came out.

in the mainframe age, FORTRAN or assembly language is typed into the computer by punching the paper tape. But this method of operation efficiency is not high, when we put a number of programmer's code into the card reader, the first to send a paper bag programmer is doing, he is waiting for this batch of programmers to pass all the tape to execute, will receive their own results, before he could not carry out his own code debugging , and his time cost has been over-consumed throughout the process. Of course, the new technology has made the hardware more resource-based in the process of suppressing programmers (this is the first batch system).

Later, in order to avoid wasting time, people developed a timeshare system (through multiple online terminals + multi-channel technology), by using the CPU High-frequency characteristics of the CPU Multi-tasking time is segmented, and every external user can use computer resources without perceiving, thus greatly speeding up the process of work (memory isolation technology is not successful, only time separation).

after that, MIT ( MIT) successfully developed a successful memory physical isolation technology, combined with the previous time-sharing system to achieve the success of the space and times of reuse, so that we have a widely used system today model.

after this, a single-user-based Unix systems are available, and many similar versions have been generated based on this version. (theUnix system only survives the small-machine era and is now the world of Linux).

5. Multi-channel technology

Multi-channel technology is the cornerstone of the operating system's implementation of batching: he means that the processor handles multiple requests for shared resources initiated by multiple programs. (implemented by Space Division Multiplexing and Time Division multiplexing)

Time Division Multiplexing:

because high CPU frequency, with the ability to quickly process transactions, so we will CPU processing time of the transaction is segmented, the previous 1S time to deal with one thing, now we define his handling N thing, N time partitioning, which can be achieved through the use of clock programs and interrupt programs to achieve a time-based reuse.

Space Division Multiplexing:

On the basis of time division multiplexing, we are destined to encounter a lot of programs to write into the memory and then physical isolation of the process, when we are large enough memory, we through the partition operation of memory, to achieve a time fragment to complete the execution of multiple tasks, it can be said that space division Multiplexing is a key link.

Combining these two technologies is the multi-channel technology we are talking about!

2017-05-19

15:54:50

Python second lesson (operating system introduction)