ostep01-Introduction to Operating Systems

ostep01-Introduction to Operating Systems

running program

a running program does one very simple thing: it executes instructions. Many millions (and these days, even billions) of times every second, the processor fetches an instruction from memory, decodes it (i.e., figures out which instruction this is), and executes it (i.e., it does the thing that it is supposed to do, like add two numbers together, access memory, check a condition, jump to a function, and so forth). 

Von Noumann Model

The Stored Program Computer

1943: ENIAC

• Presper Eckert and John Mauchly – first general electronic computer.
(or was it John V. Atanasoff in 1939?)

• Hard-wired program – settings of dials and switches.
1944: Beginnings of EDVAC

• among other improvements, includes program stored in memory
1945: John von Neumann

• wrote a report on the stored program concept,
known as the First Draft of a Report on EDVAC
The basic structure proposed in the draft became known
as the “von Neumann machine” (or model).

• a memory, containing instructions and data

• a processing unit, for performing arithmetic and logical operations

• a control unit, for interpreting instructions

参考文献
http://none.cs.umass.edu/~dganesan/courses/fall09/handouts/Chapter4.pdf

OS

• the primary way to make computer ease-to-use is virtualization
• is a resource manager
• provides system calls、API and standard libraries

Virtualization

virtualizing CPU

e.g.:running multiple program at once as if there exist many CPUs for different programs.

Virtualizing memory

e.g.:running 2 same programs simultaneously,they may be allocated the same memory address and hava the same value

Concurrency

e.g.:multithread program do not execute <font color=099ff size=5 face="΢ÈíÑźÚ">atomically</font> can lead to unexpected results

Persistence

e.g.:DRAM violate    I/O device long-lived information        hard drive、SSDfile system    open()    write()    close()    journaling    copy-on-write

Design Goals

1、abstraction2、performance，minimize the overheads of OS3、protection between applications,isolation of processes4、reliability5、energy-efficiency6、security7、mobility