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System Software

Pertemuan IVMagister Teknik Elektro

September 2008

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• The bridge between application software and computer hardware

• Imagine programming without an operating system

• what is systems software?– systems software provides a high-level environment

in which we can run applications on the computer• application software refers to word, netscape,

ultimate paint, email handlers, programs you write yourself, etc.

• note: boundary between application and systems software is not always clear

• what systems services can you think of?

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HARDWAREHARDWARE

SYSTEM SOFTWARESYSTEM SOFTWARE

APPLICATION SOFTWAREAPPLICATION SOFTWARE

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• some services of modern systems software– organizing files (folders etc)– downloading software– scheduling programs on the processor– interfacing with the internet– managing communication with peripherals– providing security– …– and lots more (GUI, windows, ...)

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early operating systems• allowed programs to be stored in computer memory

(recall architecture lecture), paving the way for batch operating systems

• users submitted programs (one instruction per punched card) and retrieve the results later

• a stack of jobs could be scheduled on the computer, hence the name "batch"

• the computer processed one job at a time• often all cards needed to be read before a program could

be started – slow!• as technology advanced, several ideas improved on the

batch operating systems:– multiprogramming allowed one program to run while another

paused, e.g. while waiting for a printer to finish– time-sharing allowed several users to run programs on a

machine, providing the opportunity for interactivity

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System software and the OSApplication Software

Application Programming Interface

Other System Software

Operating System Interface

Operating System

Software - Hardware Interface

Hardware

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MULTIPROGRAMMINGO

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SYS

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UNUSED MEMORYUNUSED MEMORY

PROGRAM 1PROGRAM 1

TRADITIONAL SINGLE-TRADITIONAL SINGLE-PROGRAM SYSTEMPROGRAM SYSTEM

OPE

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SYS

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UNUSED MEMORYUNUSED MEMORY

PROGRAM 1PROGRAM 1

PROGRAM 2PROGRAM 2

PROGRAM 3PROGRAM 3

MULTIPROGRAMMING MULTIPROGRAMMING ENVIRONMENTENVIRONMENT

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MULTITASKING

MULTIPROGRAMMING ON A SINGLE-USER SYSTEM SUCH AS A MICROCOMPUTER

*

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MULTITHREADING

ABILITY TO EXECUTE DIFFERENT PARTS (THREADS) OF A PROGRAM SIMULTANEOUSLY

*

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VIRTUAL STORAGEMETHOD 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

*

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TIME SHARINGMANY USERS SHARE LARGE CPU:• TIME IN CPU DIVIDED INTO SLICES (e.g.: 2

MICROSECONDS)• EACH USER HAS ACCESS TO CPU DURING SLICE• SINCE CPU IS FAST, CAN DO MUCH DURING

TIME SLICE• USER’S JOB SWAPPED OUT AT END OF

SLICE*

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MULTIPROCESSING• TWO OR MORE PARALLEL

PROCESSORS IN SYSTEM• PROGRAM CAN BE DIVIDED TO BE

PROCESSED BY MULTIPLE CPUs• CAN PROCESS LARGE

PROGRAMS MORE RAPIDLY *

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the unix operating system• developed in early ‘70’s at Bell Labs• innovations include

– hierarchical file system– ability to run several programs simultaneously

(timesharing)– ability to simultaneously support several users on one

computer– ability for user base to add and share tools that run as

part of the system• command line interface meant high learning

curve initially, but provides lots of flexibility to a knowledgeable user

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windows operating system

• inspired by early GUI’s developed at Xerox PARC (Palo Alto Research Center) in early 80’s

• Apple computers had earliest operating systems with windows

• Microsoft's earliest windows system was released in 1985, built on top of a command line operating system (MS DOS); the Windows became popular in 1990 with introduction of Windows 3.0

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more system software: translatingbetween programming languages

• compilers help to translate programs written in a high level programming language, such as java, into the low level machine language understood by a computer processor

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a compiler is a program whose input andoutput data are programs!

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implications of compilation

• high level programming language must be automatically translatable to low-level code

• this puts constraints on the expressiveness of computer programming languages (since computers are not very good at language processing)

• in particular, programming languages have to be very precise

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• operating system: software that coordinates and manages resources on the computer

• compiler: software that translates programs written in a high level language into a low-level language

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• 1. an application is written in a high-level programming language (e.g. java)

• 2. the code is translated to machine language (e.g. by a compiler)

• 3. when you want to run the application, the operating system loads the code into RAM (random access memory)

• 4. the fetch/execute cycle is performed

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• example

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• SOURCE CODE: HIGH-LEVEL LANGUAGE INSTRUCTIONS

• COMPILER: TRANSLATES HIGH-LEVEL CODE INTO MACHINE LANGUAGE

• OBJECT CODE: TRANSLATED INSTRUCTIONS READY FOR COMPUTER

• *

LANGUAGE TRANSLATION

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TRA

NS

LATIO

N

PR

OC

ES

S

SOURCE CODE SOURCE CODE PROGRAMPROGRAM

COMPILERCOMPILER

OBJECT CODEOBJECT CODE

LINKAGE LINKAGE EDITOREDITOR

LOAD MODULELOAD MODULE

OTHER OBJECT OTHER OBJECT CODE MODULESCODE MODULES

UTILITY PROGRAMSUTILITY PROGRAMS

PERFORM ROUTINE PERFORM ROUTINE TASKSTASKS

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GRAPHICAL USER INTERFACE (GUI)

• OPERATING SYSTEM USES:• GRAPHIC ICONS: Icons, buttons, bars,

boxes• POINTER: Mouse, pen, touch screen• TO ISSUE COMMANDS• MAKE SELECTIONS• *

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MICROCOMPUTER OPERATING SYSTEMSMICROCOMPUTER OPERATING SYSTEMS

32-bit operating system, GUI, multitasking, networking

32-bit operating system not limited to Intel chips. Multitasking, multiprocessing, networking

32-bit. Developed for IBM PS/2. Multitasking, networking

Paired-down for handheld computers, wireless communication devices

Windows Windows 98 & 9598 & 95

Windows Windows NT Me & NT Me & 20002000

Windows CEWindows CE

OS/2OS/2

OPERATING SYSTEMOPERATING SYSTEM FEATURESFEATURES

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OPERATING SYSTEMOPERATING SYSTEM

Mac OSMac OS For Macintosh computers. Multitasking. Powerful graphics, multimedia

UnixUnix For powerful microcomputers, workstations, minicomputers. Multitasking, multi-user processing, networking. Portable to various computer platforms

DOSDOS For IBM (PC-DOS) and PC (MS-DOS). Program memory: 640K

LinuxLinux Free, reliable alternative to Unix, Windows. Runs on many Platforms. Open-source

FEATURESFEATURES

MICROCOMPUTER OPERATING SYSTEMSMICROCOMPUTER OPERATING SYSTEMS

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GENERATIONS OF PROGRAMMING LANGUAGES

• 1st. Since 1940s. MACHINE LANGUAGE: binary code

• 2nd. Since early ’50s. ASSEMBLY LANGUAGE: mnemonics for numeric code

• 3rd. Since mid ‘50s. HIGH-LEVEL LANGUAGES• 4th. Since late ‘70s. MODERN APPLICATION

PACKAGES• *

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HIGH-LEVEL LANGUAGES

• FORTRAN (FORmula TRANslator): Scientific, Engineering applications

• COBOL (COmmon Business Oriented Language): Predominant for transaction processing

• BASIC (Beginners All-purpose Symbolic Instruction Code): General purpose PC language

• *

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HIGH-LEVEL LANGUAGES

• PASCAL: Used to teach structured programming practices. Weak in file handling, input / output

• C and C++: Powerful PC Language for developing applications. Efficient execution; cross platform. C++ is object oriented

• *

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FOURTH GENERATION LANGUAGES (4GL)

• CAN BE EMPLOYED BY END USERS• NONPROCEDURAL• CAN DEVELOP APPLICATIONS

QUICKLY• NATURAL LANGUAGES• SIX CATEGORIES• *

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FOURTH GENERATION LANGUAGES (4GL)

• 1. QUERY LANGUAGES:• Rapidly retrieve data• Interactive/ on-line• May use NATURAL

LANGUAGE• Support special requests for

data from relational databases*

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FOURTH GENERATION LANGUAGES (4GL)

• 2. REPORT GENERATORS:• Create customized reports• Wide range of formats

• 3. GRAPHICS LANGUAGES:• Can manipulate drawings, graphs, photos,

videos• Presentation managers *

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FOURTH GENERATION LANGUAGES (4GL)

• 4. APPLICATION GENERATORS:• User specifies computer needs• Generator creates logic and code for

application• Greatly reduces development time• *

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FOURTH GENERATION LANGUAGES (4GL)

• 5. VERY HIGH-LEVEL PROGRAMMING LANGUAGES:

• Professional programmer productivity tool

• Uses fewer instructions• Reduces development time• *

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FOURTH GENERATION LANGUAGES (4GL)

• 7. SOFTWARE PACKAGE: Commercially available set of programs...

• WORD PROCESSING• SPREADSHEETS• DATA MANAGEMENT• PRESENTATION MANAGEMENT• INTEGRATED SOFTWARE PACKAGES NOW

COMBINE THESE TO SIMPLIFY LEARNING AND USE

• *

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MIDDLEWARE

• SOFTWARE ALLOWS DIFFERENT APPLICATIONS TO EXCHANGE DATA

• *APPLICATION APPLICATION

AAAPPLICATION APPLICATION

BB

MIDDLE MIDDLE WAREWARE

DATADATA

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OBJECT-ORIENTED PROGRAMMING

• COMBINES DATA & PROCEDURES INTO A SINGLE OBJECT

• PROGRAM SENDS MESSAGE TO OBJECT TO PERFORM EMBEDDED PROCEDURE

• OBJECT’S DATA ENCAPSULATED FROM REST OF SYSTEM

• CREATES REUSABLE CODE• REDUCES TIME AND COST OF WRITING

SOFTWARE• *

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OBJECT-ORIENTED PROGRAMMING

• VISUAL PROGRAMMING: SELECT AND ARRANGE OBJECTS RATHER THAN WRITE CODE

• CLASS: ALL OBJECTS OF A CLASS HAVE ALL FEATURES OF THAT CLASS

• INHERITANCE: SPECIFIC CLASS RECEIVES FEATURES OF A MORE GENERAL CLASS

• OVERRIDE: SUBCLASS MAY OVERRIDE INHERITED METHOD (e.g.: Printout of an HOURLY worker pay check may differ from that of a WEEKLY worker

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OBJECT-ORIENTED PROGRAMMING

• JAVA: Sun Microsystems OBJECT-ORIENTED PROGRAMMING LANGUAGE

• APPLET: TINY PROGRAM TO EXECUTE SMALL FUNCTION

• APPLETS DOWNLOADED FROM NETWORK• RUN ON ANY COMPUTER & OPERATING SYSTEM• RESULT SAVED ON NETWORK, NOT ON PC• ONLY NETWORK VERSION OF SOFTWARE NEEDS

UPGRADE• *

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OBJECT-ORIENTED PROGRAMMING

• HTML: Hypertext markup language, current favorite for Web pages

• XML: eXtensible Markup Language, further development of HTML describes data more fully

• XHTML: Hybrid may replace HTML as standard for Web

• *

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OBJECT-ORIENTED PROGRAMMING

• ActiveX: Controls for Windows software environment to enable OBJECTS: e.g.,– CHARTS– TABLES– ANIMATIONS

• to be EMBEDDED IN A WEB PAGE• *