Transcript Chapter 1 - OS Overview

Chapter 1 - OS Overview
CIS106
Microcomputer Operating Systems
Gina Rue
CIS Faculty
Ivy Tech State College Northwest Region 01
Introduction
What is an operating system?
• Executive Manager - the part of the
computer that manages all of the
hardware and all of the software
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Five Major OS Components
• Memory Manager
• Processor Manager
• Device Manager
• File Manager
• User Command Interface
See Fig. 1.1 p.4
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OS Subsystem Manager Tasks
• Monitor its resources continuously
• Enforce the policies that determine who
gets what, when and how much
• Allocate the resources - reclaim it - when
appropriate
• Deallocate the resource - reclaim it when appropriate
See Figure 1.2 p.5
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OS Subsystem Managers
• Memory is in charge of main memory.
• Process decides to how to allocate the
CPU.
• Device monitors every device, channel &
control unit.
• File keeps track of every file in the
system.
See p. 6 Seven program execution steps
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Machine Hardware
• Hardware - the physical machine and its
electronic components.
• Software - instructions (programs)
written for computer systems.
• I/O devices - every physical peripheral
unit in the system.
See Fig.1.3 p.7
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Machine Hardware
• Mainframe - IBM 360, 1964. Large
physically in size and memory
• Minicomputers - Digital Equipment
Corporation, early ‘70s-. Used by smaller
institutions, schools, colleges
• Microcomputer - single user system, late
‘70’s. Targeted for small business market
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OS Types
• Batch
throughput - efficiency : measures # of
jobs completed in a given amount of time
• Interactive
• Real-time
• Hybrid
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History of OS Development
• First generation - (1940-1955)
– 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
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History of OS Development
• Second generation - (1955-1965)
– More cost effective for business environment
– Improvements: Computer operators & job
scheduling
• job 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 job
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History of OS Development
• 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 record
– Reduce discrepancy in speed between I/O and
CPU
– Spooling, program libraries, file access
methods, timer interrupts, serial batch
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History of OS Development
• 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
• interrupt - CPU notified of events needing OS
services
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History of OS Development
• Multiprogramming systems
– passive multiprogramming
– active multiprogramming
– virtual memory
– firmware
– multiprocessing
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History of OS Development
• Passive 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
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History of OS Development
• Active 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
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History of OS Development
• Virtual 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
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until needed
History of OS Development
• Firmware
– 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
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History of OS Development
• Multiprocessing
– more than one processor
– more complex languages were
designed to coordinate activities
– possible to execute programs in
parallel
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History of OS Development
• Evolution of personal computers &
high-speed communication moved on
to:
– distributed processing
– networked systems
– enabling shared hardware &
software resources from remote
locations
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Summary
• OS functions
• Evolution of increasingly complex
computers and computer systems
General Picture:
• hardware and software roles
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