Chapter 1 - OS Overview Ivy Tech State College Northwest Region 01 CIS106 Microcomputer Operating Systems Gina Rue CIS Faculty

2 Introduction What is an operating system? Executive Manager - the part of the computer that manages all of the hardware and all of the software

See Fig. 1.1 p.43 Five Major OS Components Memory ManagerMemory Manager Processor ManagerProcessor Manager Device ManagerDevice Manager File ManagerFile Manager User Command InterfaceUser Command Interface

See Figure 1.2 p.54 OS Subsystem Manager Tasks Monitor its resources continuouslyMonitor its resources continuously Enforce the policies that determine who gets what, when and how muchEnforce the policies that determine who gets what, when and how much Allocate the resources - reclaim it - when appropriateAllocate the resources - reclaim it - when appropriate Deallocate the resource - reclaim it - when appropriateDeallocate the resource - reclaim it - when appropriate

See p. 6 Seven program execution steps5 OS Subsystem Managers Memory is in charge of main memory.Memory is in charge of main memory. Process decides to how to allocate the CPU.Process decides to how to allocate the CPU. Device monitors every device, channel & control unit.Device monitors every device, channel & control unit. File keeps track of every file in the system.File keeps track of every file in the system.

See Fig.1.3 p.76 Machine Hardware Hardware - the physical machine and its electronic components.Hardware - the physical machine and its electronic components. Software - instructions (programs) written for computer systems.Software - instructions (programs) written for computer systems. I/O devices - every physical peripheral unit in the system.I/O devices - every physical peripheral unit in the system.

7 Machine Hardware Mainframe - IBM 360, Large physically in size and memoryMainframe - IBM 360, Large physically in size and memory Minicomputers - Digital Equipment Corporation, early ‘70s-. Used by smaller institutions, schools, collegesMinicomputers - Digital Equipment Corporation, early ‘70s-. Used by smaller institutions, schools, colleges Microcomputer - single user system, late ‘70’s. Targeted for small business marketMicrocomputer - single user system, late ‘70’s. Targeted for small business market

8 OS Types BatchBatch throughput - efficiency : measures # of jobs completed in a given amount of time InteractiveInteractive Real-timeReal-time HybridHybrid

9 History of OS Development First generation - ( )First generation - ( ) –Assemblers/Compilers translate binary code & English-like commands –System software, macros, programs, utility program and device driver creation – Device driver subroutines written to standardize input and output

10 History of OS Development Second generation - ( )Second generation - ( ) –More cost effective for business environment –Improvements: Computer operators & job scheduling job scheduling - groups together programs with similar requirementsjob scheduling - groups together programs with similar requirements – (JCL) Job Control Language assists OS manage system resources by identifying users and their jobs, and specify resources to execute each jobassists OS manage system resources by identifying users and their jobs, and specify resources to execute each job

11 History of OS Development Improved CPU performance (2nd gen. cont.)Improved CPU performance (2nd gen. cont.) –Speed of I/O devices –Use more available storage by blocking records before retrieval and storage Blocking - several logical records grouped within one physical recordBlocking - several logical records grouped within one physical record –Reduce discrepancy in speed between I/O and CPU –Spooling, program libraries, file access methods, timer interrupts, serial batch

12 History of OS Development Third generation - (mid-1960s)Third generation - (mid-1960s) –Designed with faster CPU –Relatively slow I/O devices –Solution multiprogramming concept of many programs sharing the attention of a single CPU concept of many programs sharing the attention of a single CPU interrupt - CPU notified of events needing OS servicesinterrupt - CPU notified of events needing OS services

13 History of OS Development Multiprogramming systemsMultiprogramming systems –passive multiprogramming –active multiprogramming –virtual memory –firmware –multiprocessing

14 History of OS Development Passive MultiprogrammingPassive Multiprogramming –OS didn’t control interrupt –OS waited for each job to end –Ideal for nonstop processing before issuing an interrupt “CPU-bound” –It would tie up the OS for long periods of time

15 History of OS Development Active MultiprogrammingActive Multiprogramming –allows each program to use a slice of time –when time expired, the job was interrupted by another job –each interrupt job had to wait its turn

16 History of OS Development Virtual MemoryVirtual Memory –took advantage of the fact that the CPU could only process one instruction at a time –the entire program didn’t have to reside in memory before execution –divides the programs into segments keeping them in secondary storage until needed

17 History of OS Development FirmwareFirmware –OS was made part of hardware –a program is permanently held in ROM (read only memory) –many programming functions were being carried out by the OS –made programmer’s task simpler

18 History of OS Development MultiprocessingMultiprocessing –more than one processor –more complex languages were designed to coordinate activities –possible to execute programs in parallel

19 History of OS Development Evolution of personal computers & high-speed communication moved on to:Evolution of personal computers & high-speed communication moved on to: –distributed processing –networked systems –enabling shared hardware & software resources from remote locations

20 Summary OS functionsOS functions Evolution of increasingly complex computers and computer systemsEvolution of increasingly complex computers and computer systems General Picture: hardware and software roleshardware and software roles