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PRACTICAL APPROACHOF OPERATING SYSTEM
CSC204
Chapter 1.1:
Uner!tan"n# OS
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#
1.1 UN$ERSTAN$ING
OS
1.1.1 %hat "! OS&
1.1.2 H"!t'r( ') OS
$e*e+'p,ent1.1.- T(pe! ') OS
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1.1Uner!tan"n# OS
1.1.1 %hat "! OS&
An OS is a program that acts as an intermediarybetween a user of a computer and the
computer hardware Operating system goals:
Execute user programs and make solving userproblems easier.
Make the computer system convenient to use
An operating system uses the computerhardware in an ecient manner
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A computer system can be divided roughlyinto:
!. Harare " provides basic computingresources for the system
#. Operat"n# !(!te, " controls andcoordinates the use of the hardware among
the various application programs for thevarious users
$. App+"/at"'n! pr'#ra,! " de%ne the waysin which the system resources are used to
solve the computing problems of the users
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A!tra/t "e ') S(!te, C',p'nent!
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Operating System Main 'unctions
Re!'r/e a++'/at'r " manages andallocates resources
C'ntr'+ pr'#ra, " controls the execution ofuser programs and operations of ()O devices
3erne+ " the one program running at alltimes on the computer *along with the kernel+there are # other types of programs: systemprograms and application programs,
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(n general+ acomputer systemhas some resourceswhich may beutili-ed to solve aproblem. hey are Memory
0rocessor*s,
()O
'ile System
etc.
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he OS ,ana#e! the!e re!'r/e! ana++'/ate! the,to speci%c programs andusers.
1ith the management of the OS+ aprogrammer is rid of dicult hardwareconsiderations.
An OS pr'*"e! !er*"/e! for0rocessor Management
Memory Management'ile Management2evice Management3oncurrency 3ontrol
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1.1.2 H"!t'r( ') OS $e*e+'p,ent
'irst generation !4&5 6 !455
echnology: *a/, te! p+#'ar! 0rogramming: !ett"n# !',e !"t/he!
0rogramming language: ,a/h"ne +an#a#e
asks: ta+e! ') !"ne5 /'!"ne5 +'#ar"th,!
OS: n'ne
3omputer designer is: builder and
programmer and
operator and
sys admin 4
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Second generation !455 !475 echnology: Tran!"!t'r! 0rogramming: Pn/he /ar! 0rogramming languages: FORTRAN A!!e,+(
asks: S/"ent"6/ 3omputer: Ma"n)ra,e! OS: 7at/h !(!te,
8niversities started to buy computers
*millions 9, Separation between computer designers+
builders+ operators+ programmers andmaintenance personnel.
!
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Second generation !455 !475 echnology: Tran!"!t'r! 0rogramming: Pn/he /ar! 0rogramming languages: FORTRAN A!!e,+(
asks: S/"ent"6/ 3omputer: Ma"n)ra,e! OS: 7at/h !(!te,
8niversities started to buy computers
*millions 9, Separation between computer designers+
builders+ operators+ programmers andmaintenance personnel.
!!
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hird generation !475 " !4; echnology: IC! 0rogramming: Pn/he /ar!
0rogramming languages: FORTRAN A!!e,+( asks: S/"ent"6/ /',,er/"a+ 3omputers: I7M -805 $EC P$P!
OS: M+t"pr'#ra,,"n#9t",e!har"n#5 !p''+"n#
OSes 2eveloped: MULTICS (father of all modern OSes) UNIX (System V, BSD)
POSIX (y I!!!)
MINIX (y Tanena"m)
L#n"$ (der#%ed from MINIX) !#
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'ourth generation !4;60resent echnology: LSI
0rogramming: H"#h +e*e+
0rogramming languages: C9C5 ;a*a5
3omputer: PC
OS: %"n'!5 Ma/OS5 L"n<
3heap 03s
!$
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!.!.$ ypes of OS
a, ybride, Embedded
!&
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a= 7at/h
A batch system is one in which ?obs arebundled together with the instructionsnecessary to allow them to beprocessed without intervention.
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!7
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bring cards to (
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=T",e Shar"n#9Intera/t"*e
ime sharing is a logical extension ofmultiprogramming.
(n time sharing systems+ the 308executes multiple ?obs by switchingamong them+ but the switches occur so
freBuently that the users can interactwith each program while it is running.
(t reBuires an interactive computersystem providing direct communication
between user and the system !@
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/= Rea+>T",e
An OS that guarantees a certaincapability within a speci%ed timeconstraint.
his can be especially important inmeasurement and automation systems
where downtime is costly or a programdelay could cause a safety ha-ard.
E.g. industrial process control systemswhere each ?ob must be completed in
the speci%ed time. !;
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e= H(r"
A
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e= E,ee
An e,ee 'perat"n# !(!te,! is OSfor embedded computer system.
hese operating systems are designed tobe compact+ ecient+ and reliable for manyfunctions.
irtually all appliances that have a digitalinterface. E.g: watches+ microwaves+ 3=s+cars 66 utili-e embedded systems.
Some embedded systems include an
operating system. #
1.1Uner!tan"n# OS
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