"Linux_ Notes"-Operating system basics

Common CPU Series (Hardware architecture):

1, ARM (mobile hardware platform): Only the production of intellectual property does not produce equipment, only responsible for the design of chips, the real production are by Samsung Qualcomm these production. Handheld smart devices are part of the hardware architecture of arm.
2, x86: refers to the Intel or AMD x86 series, 32-bit platform
--32-bit and 64-bit operating systems refers to whether the CPU is capable of processing data 32-bit or 64-bit at a time
-that is, the difference between 32 lanes in parallel and 64 lanes in parallel, so that 64-bit traffic can be much larger than the 32-bit one.
3, x64:
4. Itanium: Intel Intel did not have a 64-bit CPU and AMD has already appeared, under the premise of acquisition from HP.
5. Alpha: Hewlett-Packard (Itanium sold to Intel)
6. ULTRASPARC (High performance CPU): Sun (already acquired by Oracle) was designed by Stanford University and later transferred to Sun, which is produced by Fujitsu on its behalf.
7, Power (the world's first dual core eight core 64 core CPU, and is the first CPU with a frequency of more than 4GHz): IBM
8, M68000 (m68k): Motorola
9, PowerPC (less than power, but the performance is still very good CPU): Apple/ibm/Motorola
......

(Linux is all over the corner, because Linux almost supports all of these CPU types)

Operating System ( OS):

Windows
Linux
Unix
HP-UX: Hewlett-Packard
Solaris:sun
Aix:ibm
SCO Unix:sco
UnixWare ...
Os/2

Batch processing:

Job: A complete computational process that runs on a computer we call it a job, an early job on tape, a job on each tape, a job done, and a tape down for another tape. Later, in order to improve speed, to put multiple jobs on a tape, multiple jobs are separated by some separators.
Jobs:job1&&&&&&&&job2
Multitasking system: During the execution of a job, the execution of a command, because the computer's CPU speed is too fast, most of the time in order to interact with the IO is idle, because the computing power is very expensive, so people want to do It is possible to get the CPU busy and want multiple programs to run simultaneously, meaning that to divide a resource into multiple resources, you need to cut two important components (cpu,memory) in the process of running the computer.
Process: A running program called a process (the process is a life cycle-from start to finish)
Workflow of the process:
1, the CPU to cut:
Slice (time slice of CPU)
5ms (assuming the run time of the first program)
5ms (assuming the run time of the second program)
2. Cut the Memory:
Fragmentation mechanism: For example, the memory is divided into two paragraphs 1, 2, the first program from the first paragraph of 001, the second program starts from the second paragraph of 001-relative address
Each program runs with its own virtual address space (the programmer develops the program regardless of physical memory, such as on a 32-bit system, assuming 4G memory is available--2^32).
In this process need to have software to monitor the operation of the program (give you 5ms you can only run 5ms ... )--The operating system is the complete mechanism.

Operating system (generic software, not responsible for the specific work, it is only responsible for coordinating the work of other specific procedures): Software running on hardware, responsible for the management of hardware resources, but also the hardware resources provided by cutting into several pieces of computing power, divided into multiple different programs, memory into multiple section, to a number of different programs, and coordination between them, the operating system is also responsible for the completion of a program start, termination and recovery work, but also responsible for the program switching and so on. So this kind of software can also have multiple, this is why there are windows,linux and other operating systems exist simultaneously reason

The operating system itself is a generic software, this software installed, the entire hardware itself provides the computing power to use the form of software simulation, as two times the simulation, so any program see is not the hardware itself but the interface provided by the operating system, the operating system of this function interface in order to be able to do Possible simplification, do very low-level, the interface of the operating system is called system call (Systems calls), with the operating system, no program can directly deal with the hardware, to use the hardware function must be through the operating system, through the operating system to coordinate.

Programs that you can run under Windows do not necessarily run under Linux.

For example, write a C program, in Windows down with the windows provided by the C library to program the Linux downgrade with Linux provided by the C library to program, if the two libraries are different, then the program can not run under Linux, even if the two libraries are the same, not necessarily enough to run.
Library APL: The role of bridging the underlying hardware is different, is a bunch of programs, the library does not execute the portal (such as Main in C), can be executed by other programs, provide a unified calling interface call.
Programmer development programs (such as using C to write) are written by call, a process that invokes the functionality provided by others and then develops the program.

The bottom of the understanding: for example, to make a steamed bread, give you a pile of wheat, you have to take the wheat back to grind into flour and then fermented into steamed bread, or directly to you steamed bread. Wheat and steamed bread, wheat is the bottom, give you wheat you can make steamed bread you can also make buns ..., and steamed buns cannot be reduced to flour. So the bottom of the operating system will be the upper level of the programmer to determine its application mechanism, the lower the bottom means that its mechanism changes less, the operating system in order to simplify its function, simplify its call interface, function interface do Very low ground.
Library APM: In order to facilitate the call of the programmer, someone is specifically responsible for the system call once again encapsulated, make it more powerful, just like someone with wheat will steamed buns are done, you want what you buy anything on the line. These encapsulate the functionality called by one or more underlying systems and make the more advanced interface The library APL.

This article from "Not Daze" blog, please make sure to keep this source http://tobeys.blog.51cto.com/10620284/1685896

"Linux_ Notes"-Operating system basics