CSI 400/500 Operating SystemsSpring 2009

Lecture #2 – Functional Parts of an Operating System

Monday January 23, 2009

The Manager

Device ManagerCommunicates with devicesMaintains driversAllocates portsPasses data and signals between

device and taskDiscussed in detail in Lecture 14

Process SpoolerSchedules tasksAllocates resourcesMaintains process isolation while

providing contact with system

Our next topic

Memory ManagerAllocation of resources across systemSeparates memoryTranslates virtual addresses

Discussed in Lectures 8 and 9

File ManagerMaintains links to external storage

devicesMaintains internal files and mapsHandles data transfer between tasks

and files

Discussed in Lectures 10 and 11

Interrupt HandlerAnalyzes errorsPauses action to prevent further

problemsFixes error or terminates actionCommunicates with Process Manager

Discussed in Lecture 14

System CallsStored library of functionsPasses messages between functionary

partsAvailable system-wideSome available to user-defined tasks

OS Concerns

Security ConcernsWithin systemBetween tasks and processesFrom outside

Discussed at end of course

OS Components

Central Processing UnitCalled “Processor”Performs calculations and operationsTwo parts:

Arithmetic-logical unit Control unit and program counter

RegistersLocal to processorHolds single value or addressTypes:

Memory address register Memory data register Command register Instruction register Operation data registers

Instruction StackHeld in local memoryHolds instructions and related operandsSequentialOne instruction at a time loaded into

CPU for processing

BusesUsed to transfer info:

Between tasks Between units Between systems

High-speedDumb

Input/Output ControllersDevice driversConnected by ports, channels, or bus

linesControls flowDOES NOT handle data transfer

Handled by task Managed by device

Interrupt LibraryCatalog of interruptsAvailable to all unitsCommon and categorizedRecognized by Interrupt handler