cs481 operating systems

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CS481Operating Systems

Prof. Cris Pedregal - cris@cs.unm.edu

Textbook: Tanenbaum MOS 2ED

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Learning: a social activity• you learn through your own work

• be a good student and classmate– make friends early, help each other

• you can (get/give) help without cheating

– come to class ready to work• ask questions and let others ask; be patient

• turn off your cellphone, personal stereo, etc.

• knowledge, competence, confidence

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Introduction

Chapter 1

1.1 What is an operating system1.2 History of operating systems1.3 The operating system zoo1.4 Computer hardware review1.5 Operating system concepts1.6 System calls1.7 Operating system structure

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Introduction

• A computer system consists of– hardware

– system programs

– application programs

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What is an Operating System

• It is an extended machine– Hides the messy details which must be performed

– Presents user with a virtual machine, easier to use

• It is a resource manager– Each program gets time with the resource

– Each program gets space on the resource

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History of Operating Systems (1)

Early batch system– bring cards to 1401– read cards to tape– put tape on 7094 which does computing– put tape on 1401 which prints output

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History of Operating Systems (2)

• First generation 1945 - 1955– vacuum tubes, plug boards

• Second generation 1955 - 1965– transistors, batch systems

• Third generation 1965 – 1980– ICs and multiprogramming

• Fourth generation 1980 – present– personal computers

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History of Operating Systems (3)

• Structure of a typical FMS job – 2nd generation

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History of Operating Systems (4)

• Multiprogramming system– three jobs in memory – 3rd generation

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The Operating System Zoo

• Mainframe operating systems

• Server operating systems

• Multiprocessor operating systems

• Personal computer operating systems

• Real-time operating systems

• Embedded operating systems

• Smart card operating systems

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Computer Hardware Review (1)

• Components of a simple personal computer

Monitor

Bus

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Computer Hardware Review (2)

(a) A three-stage pipeline(b) A superscalar CPU

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Computer Hardware Review (3)

• Typical memory hierarchy– numbers shown are rough approximations

– but ratios are more important anyway

– still, what’s wrong with this picture?

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Computer Hardware Review (4)

Structure of a disk drive

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Computer Hardware Review (5)

One base-limit pair and two base-limit pairs

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Computer Hardware Review (6)

(a) Steps in starting an I/O device and getting interrupt(b) How the CPU is interrupted

(a) (b)

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Computer Hardware Review (7)

Structure of a large Pentium system

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Summary Hardware Review

• Exists in real world, subject to constraints:– e.g., disk latency limited by spin speed

– wiring limits determine bus width/speed

• Different hardware components:– relative costs, speeds, determine architecture

– architecture constrains/induces OS

– tradeoffs induce complexity

– tradeoffs change with time

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Operating System Concepts (1)

• A process tree– A created two child processes, B and C

– B created three child processes, D, E, and F

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Operating System Concepts (2)

(a) A potential deadlock. (b) an actual deadlock.

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Operating System Concepts (3)

File system for a university department

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Operating System Concepts (4)

• Before mounting,– files on floppy are inaccessible

• After mounting floppy on b,– files on floppy are part of file hierarchy

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Operating System Concepts (5)

Two processes connected by a pipe

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Summary: OS Concepts

• Processes– Resources, Deadlocks

– Pipes

• Memory Management

• Input/Output

• Files

• Security

• The Shell

• Concept Recycling

• layers = abstraction• policies and

mechanisms• user versus supervisor

(kernel) mode– different spaces– different levels of

executions andprivileges

– system calls (kernel)application codelibrary code