PART I Introduction to the Foundation of information Technologies Session 7 Computer Software
HUANG Lihua, Fudan University Session 7 Computer Software PART I Introduction to the Foundation of Information Technologies
SOFTWARE 软件是计算机的灵魂” PROGRAM: Set of instructions to the computer STORED: Program must be in primary storage Software: Detailed instructions to control computer operation of a computer systems. Without software, the computer hardware could not perform any tasks. The functions of software are to (1) manage the computer resources of the organization, (2 provide tools for human beings to take advantage of the these resources ()act as intermediary between organizations and stored information
HUANG Lihua, Fudan University • PROGRAM: Set of instructions to the computer • STORED: Program must be in primary storage • Software: Detailed instructions to control computer operation of a computer systems. Without software, the computer hardware could not perform any tasks.The functions of software are to – (1) manage the computer resources of the organization, – (2) provide tools for human beings to take advantage of the these resources – (3) act as intermediary between organizations and stored information. SOFTWARE “ 软件是计算机的灵魂
SOFTWARE APPLICATION SOFTWARE Generalized programs that SYSTEM SOFTWARE manage the resources of the computer, including Operating System: HARDWARE scheduled computerevent .Allocates computer resources .Monitors events -Language translators .Interpreters Compilers -Utility Programs: .Routine operations Manage data Programs written for a specific application to perform functions specified by end users -Programming Language -software package
HUANG Lihua, Fudan University Programs written for a specific application to perform functions specified by end users. -Programming Language -software package APPLICATION SOFTWARE Generalized programs that manage the resources of the computer, including -Operating System: •Scheduled computer event •Allocates computer resources •Monitors events -Language translators: •Interpreters •Compilers -Utility Programs: •Routine operations •Manage data SYSTEM SOFTWARE SOFTWARE HARDWARE
Operating system Allocates and assigns memory >e.g, file system, virtualmemory processor time >e. g, multitasking, multiprocessing input-output devices >e.g, printer, keyboard, etc. May also provide other capabilities useful to many users or programs Graphical User Interface(GUn) capabilities Fonts, network protocols
HUANG Lihua, Fudan University Operating system • Allocates and assigns: – memory » e. g., file system, virtual memory – processor time » e. g., multitasking, multiprocessing – input- output devices » e. g., printer, keyboard, etc. • May also provide other capabilities useful to many users or programs – Graphical User Interface (GUI) capabilities – Fonts, network protocols,
Operating system as magician(魔术师) The four illusions Many separate computers, one for each process < Multitasking Large memory -Virtual memory Disks and other secondary storage are organized as collections of files-"File systems Windows and menus-"Graphical User Interface(GUD)
HUANG Lihua, Fudan University Operating system as magician(魔术师） • The four illusions – Many separate computers, one for each process – “Multitasking” – Large memory – “Virtual memory” – Disks and other secondary storage are organized as collections of files – “File systems” – Windows and menus – “Graphical User Interface (GUI)
OOperating Systems Capabilities: Multiprogramming. Multitas king TRADITIONAL SINGLE- MULTIPROGRAMMING PROGRAM SYSTEM ENVIRONMENT PROGRAM 1 PROGRAM 2 PROGRAM 1 9zu z PROGRAM 3 UNUSED MEMORY UNUSED MEMORY
HUANG Lihua, Fudan University Operating Systems Capabilities: Multiprogramming, Multitasking OPERATING SYSTEM UNUSED MEMORY PROGRAM 1 TRADITIONAL SINGLEPROGRAM SYSTEM OPERATING SYSTEM UNUSED MEMORY PROGRAM 1 PROGRAM 2 PROGRAM 3 MULTIPROGRAMMING ENVIRONMENT
crating Systems Capabilities Virtual storage Virtual Storage is the method of handling several programs in primary storage Program divided into Fixed length portions(pages) OR Variable length(segments) Current portions reside in primary storage, portions swapped out when done
HUANG Lihua, Fudan University Operating Systems Capabilities: Virtual Storage • Virtual Storage is the method of handling several programs in primary storage: – Program divided into • Fixed length portions(pages) OR • Variable length (segments) – Current portions reside in primary storage, portions swapped out when done
erating Systems Capabilities: time sharing MANY USERS SHARE LARGE CPU Time in CPu divided into slices(e.g: 2 microseconds) Each user has access to cpu during slice Single CPU is fast, can do much during time slice Users job swapped out at end of slice
HUANG Lihua, Fudan University Operating Systems Capabilities: time sharing MANY USERS SHARE LARGE CPU: • Time in CPU divided into slices (e.g.: 2 microseconds) • Each user has access to CPU during slice. • Single CPU is fast, can do much during time slice • User’s job swapped out at end of slice
crating Systems Capabilities Multiprocessing Links together two or more CPUs to work in parallel in a single computer systems to execute two or more instructions Program can be divided to be processed by multiple cPus Can process large programs more rapidly
HUANG Lihua, Fudan University Operating Systems Capabilities: Multiprocessing • Links together two or more CPUs to work in parallel in a single computer systems to execute two or more instructions. – Program can be divided to be processed by multiple CPUs. – Can process large programs more rapidly *
(operating Systems Capabilities File Systems Reality: Disks are sets of tracks(磁道) Tracks are sets of sectors(扇区) Sectors can store fixed- sized byte blocks illusion: Disks are sets of directories(目录) Directories contain other directories or files Files are variable- size byte sequences Directories and files have names
HUANG Lihua, Fudan University Operating Systems Capabilities: File Systems • Reality: – Disks are sets of tracks(磁道） – Tracks are sets of sectors（扇区） – Sectors can store fixed- sized byte blocks • Illusion: – Disks are sets of directories （目录） – Directories contain other directories or files – Files are variable- size byte sequences – Directories and files have names