What is an operating system?

1
What is an operating system?
CSC330 Patricia Van Hise
2

• What are the components of a computer system?

3
What is an Operating System?

• A program that acts as an intermediary between a
  user of a computer and the computer hardware.
• Operating system goals
• Execute user programs and make solving user
  problems easier.
• Make the computer system convenient to use.
  (User interface, API)
• Use the computer hardware in an efficient manner.
  

4
A Computer System
5
Functions of an OS

• Interface
• Acts as an abstract virtual machine
• Hides the details from user
• Control execution of programs and operations of
  control devices
• Resource manager
• Maximize system utilization and/or performance
• Time and space
• Sharing of limited or expensive physical
  resources
• Provides Protection
• File storage, network communications, etc.

6
History of Operating Systems

• 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

7

• Structure of a typical FMS job 2nd generation

8

• Multiprogramming system
• three jobs in memory 3rd generation

9
Todays Range of Operating Systems

• Mainframe operating systems
• Server operating systems
• Multiprocessor operating systems
• Personal computer operating systems
• Real-time operating systems
• Embedded operating systems
• Smart card operating systems

10
Migration of Operating-System Concepts and
Features
11
Computer Hardware Review
Bus
Components of a simple personal computer
12
The Von Neumann Cycle and Beyond
(a) A three-stage pipeline (b) A superscalar CPU
13
Typical memory hierarchy

• numbers shown are rough approximations

14
One base-limit pair and two base-limit pairs
15
Computer Hardware
Structure of a disk drive
16
Structure of a large Pentium system
17
Input/Output

• An I/O device consists of two parts
• Controller - chip that physically controls the
  device

• The device itself

(The controller presents a simple interface to
the operating system.)

• The software needed for each I/O device is called
  a driver.

• A driver gives commands to the controller and
  accepts its responses, and must run in kernel
  mode as part of the o.s.
• A device must have a different driver for each
  operating system it supports.

18
3 Methods of I/O
Programmed I/O
n
n
Interrupt driven
n
n
n