1 What is an operating system? CSC330Patricia Van Hise

2   What are the components of a computer system? A computer system consists of hardware system programs application programs

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 vacuum tubes, plug boards Second generation transistors, batch systems Third generation 1965 – 1980 ICs and multiprogramming Fourth generation 1980 – present personal computers

7  Structure of a typical FMS job – 2 nd generation

8  Multiprogramming system  three jobs in memory – 3 rd generation

9 Today’s 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 (a) A three-stage pipeline (b) A superscalar CPU The Von Neumann Cycle and Beyond

13 numbers shown are rough approximations Typical memory hierarchy

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 Driver starts I/O and polls device to see if done; Busy wait Interrupt driven Driver starts device; driver returns control to OS. OS blocks the caller and looks for other work to do. Device sends a signal, or interrupt, to the OS to indicate completion. OS then unblocks caller. Direct Memory Access (DMA) - for high-speed I/O - transfers entire block of data with 1 interrupt rather than 1 interrupt per byte.