1. Basic Operating System Concepts

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Basic Operating

System Concepts

Ami Tri Cahyadi


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Toleransi Keterlambatan : (maks) 15menit

Presensi (kehadiran) : (min) 80%

Komponen Penilaian :

Presensi : 10%Kuis : 10%

Tugas : 30%

UTS : 25%

UAS : 25%


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Learning materials

1.Introduction to Operating Systems

2.Basic Operating System Concepts

3.Process Management

4.Interprocess Communication & Synchronization5.Memory Management

6.File System Management

7. Device Management


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Reference :

Stallings, William, Operating Systems, SecondEdition, Prentice-Hall International Editions,Englewood Cliffs, New Jersey, 1995.

Tanenbaum, Andrew S., Modern OperatingSystems, Prentice-Hall International Editions,Englewood Cliffs, New Jersey, 1992.


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Personal Computer OSMobile DevicesServer

Embedded Devices


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What is an Operating

System?

An Operating systemis basically a intermediaryagent between the user and the computerhardware.

Manages the computers resources (hardware,abstract resources, software)

Its a resource allocator.It is also used to control programs to prevent errors

and improper computer use.It is interrupt driven.


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Operating System Benefits

Simplifies hardware control forapplications

Enforcer of sharing, fairness andsecurity with the goal of better overall

performanceTrade-off between fairness and

performanceTrade-off between optimal algorithms and

lean algorithms OS is overhead.Provides abstract resourcesSocketsInter-process communication


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History of Operating

Systems

Earliest computers had no Operating SystemApplications loaded manually

Users were experts on the hardwareFirst System Softwarewas libraries of codeto manage devices.

This grew to batch processing systems, wheresome focused on application programming and

some on systems programming.


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Timesharing

A timesharing systemallows multipleusers to interact with a computer atthe same time

Multiprogrammingallowed multipleprocesses to be active at once, whichgave rise to the ability for programmersto interact with the computer system

directly, while still sharing its resourcesIn a timesharing system, each user has

his or her own virtual machine, in which


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The IBM 650 Magnetic

Drum Data ProcessingSystem Machine

Cray I supercomputer,

introduced in 1976


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Current Operating Systems

Research Topics

Symmetric multiprocessing

Allows for several CPUs to process multiple jobs at the sametime. CPUs are independent of one another, but each hasaccess to the operating system.Asymmetric multiprocessing

Some operating systems functions are assigned tosubordinate processors, which take their instructions fromthe main CPU.Distributed processing

Processors are placed at remote locations and are connectedto each other via telecom devices. Different from symmetric

multiprocessing systems as they do not share memory.Computations can be dispersed among several processors.


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COMPUTER

ARCHITECTURE

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The computer is in a sense a communication system.Data is constantly being moved between the CPU,

memory and the various devices.The CPU uses I/O addresses to direct data to

particular devices.The devices in turn use interrupts to notify theCPU and operating system of their needs.


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The Von-Neumann

Architecture


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CPU Control Unit


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Arithmetic Logic Unit


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The Von-Neumann Loop

Fetch hase

Fetch the next instruction and store it in the

instruction registerExecute hase

The ALU or I/O unit executes the instructionALUdoes calculationsI/O unitloads or stores data between

main memory and registers


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How Operating

Systems Work

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Role of Interrupts

Interrupts are signals sent to the CPU by external devices, normally I/Odevices. They tell the CPU to stop its current activities and execute theappropriate part of the operating system.

1.Hardware Interuptsare generated by hardware devices to signal that they

need some attention from the OS.2.Software Interuptsare generated by programs when they want to requesta system callto be performed by the operating system.3.Traps are generated by the CPU itself to indicate that some error orcondition occured for which assistance from the operating system is needed.


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CPU Execution Mode

There are two modes of execution,known as user mode and kernel orsupervisor mode.

User mode is restricted in that certaininstructions cannot be executed, certainregisters cannot be accessed, and I/Odevices can not be accessed.

Kernel mode has none of theserestrictions. A system callwill set theCPU to kernel mode, as will traps and

.


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Supervisor modeCan execute all machineinstructionsCan reference all memory

locations

User modeCan only execute a subset ofinstructions

Can only reference a subsetof memory locations


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CPU Response to

Interrupts

The CPU performs the followingactions in response to an interrupt:

Using the pointer to the current processcontrol block, the state and all registervalues for the process are saved for usewhen the process is later restarted.

The CPU mode bit is switchedto supervisorymode.

Using the pointer to the interrupthandler table and the interrupt vector, thelocation of the kernel code to execute isdetermined. The interru t vector is the IRQ


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Interrupt Processing


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PARTS OF OPERATING

SYSTEM

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rocess Management

Aprocessis an executing program. It hasits code, data, a certain set of resourcesallowed to it, and one or more flows ofexecution through the code.The OS manages the allocation of resourcesto these processes, and also provides

system calls to manage these processes.


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Memory Management

Memory must be shared between the OS and anapplication program.The OS must manage the allocation of memory toprocesses and control the memory managementhardware that determines which memory locations aprocess may access.


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File System Management

Computers process information that must betransmitted, processed, or stored.

File systems are an abstract organized collection offile system objects.The OS provides primitives to manipulate theseobjects


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Device Management

Information is sent through a computersinput and output devices.

Processes access these devices using

the system callinterface.The OS tries to manage said devices in a

manner that makes them efficiently sharedamong all processes requiring them.

A system callis a programming interfaceto the services provided by the OS,typically written in C/C++


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Evolution of an

Operating System


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Hardware upgrades plus new types ofhardware

New services & ToolsFixes: Any OS has faults. These are

discovered over the course of time andfixes are made.


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Documents

1. Basic Operating System Concepts