os chapter1 os chapter1, Cheat Sheet of Operating Systems

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Chapter 1

Computer System Overview

Manatee Community College, Venice,^ Patricia Roy ©2008, Prentice HallFL

Operating Systems: Internals and Design Principles, 6/E William Stallings

Operating System

• Exploits the hardware resources of one or more processors
• Provides a set of services to system users
• Manages secondary memory and I/O devices

Basic Elements

• Processor
  • I/O address register
  • I/O buffer register

Basic Elements

• Main Memory
  • Volatile
  • Referred to as real memory or primary memory

Computer Components: Top-

Level View

Processor Registers

• User-visible registers
  • Enable programmer to minimize main memory references by optimizing register use
• Control and status registers
  • Used by processor to control operating of the processor
  • Used by privileged OS routines to control the execution of programs

User-Visible Registers

• Data
  • Data register: is the same of memory buffer register
• Address
  • Index register: Adding an index to a base value to get the effective address
  • Segment pointer: When memory is divided into segments, memory is referenced by a segment and an offset
  • Stack pointer: Points to top of stack

Control and Status Registers

• Program counter (PC)
  • Contains the address of an instruction to be fetched
• Instruction register (IR)
  • Contains the instruction most recently fetched
• Program status word (PSW)
  • Contains status information

Instruction Execution

• Two steps
  • Processor reads (fetches) instructions from memory
  • Processor executes each instruction

Basic Instruction Cycle

Instruction Register

• Fetched instruction loaded into instruction register
• Categories
  • Processor-memory, processor-I/O, data processing, control

Example of Program Execution

Classes of Interrupts

Program Flow of Control