CHAPTER 2

• system architecture - is the structure, interaction and technology of computer system components
• capabilities of computer

  • accept numeric inputs
  • perform computational functions
  • communicate results
• automated computation

  • mechanical - early computers with limited capabilities
  • electronic - fast, accurate, reliable
  • optical - fast, accurate, reliable
• mechanical implementation - mechanical representation of a mathematical calculation
• limitations and shortcomings of mechanical implementation

  • complex design and construction
  • wear, breakdown and maintenance of parts
  • limits on operating speed
• the difference engine - 1821 by charles babbage
• electronic implementation - stores values as magnetic charges or by positioning electrical switches
• electrical implementation - faster, more reliable, easier to build than mechanical counterparts
• optical implementation - harnesses energy of a moving photon
• optical implementation - now common in computer networks that cover large distances
• quantum computing - computing based on quantum mechanics, somewhat controversial, not yet shown to be usable
• computer capabilities

  p s c

  • processing
  • storage
  • communication
• processor - device that performs data manipulation and transformation functions
• processor types

  • general purpose
  • special purpose
• storage capacity - typ of storage that can be used to store data, such as RAM, hard disk, or optical disk
• types of information to be stored

  • intermediate processing results
  • data
  • programs
• characteristics of storage devices vary widely

  c as R

  • cost
  • access speed
  • reliability
• components of computer system

  A) primary storage

  B) secondary storage

  C) input output unit

  D) CPU

  E) users

  F) computers

  
• CPU components

  • ALU
  • registers
  • control unit
• ALU - contains electrical circvuits that implement each inteructions
• registers - internal storqage locations that can hold a single instruction or data item
• control unit - controls the movements of data from CPU
• system bus - internal communication channel that connects all other hardware devices
• primary storage - holds program instructions and data for currently executing programs
• secondary storage - composed of high capacity nonvolatile storage devices that hold programs and data
• input and output devices - implement external communication functions
• computer system classes

  • microcomputer
  • midrange computer
  • mainframe computer
  • supercomputer
• microcomputer - meets information processing needs of single user
• midrange computer - supports many programs and users simultaneously
• mainframe - handles information processing needs of large number of user and application
• supercomputer - designed for rapid mathematical comutation
• multicomputer configurations - any organizations of multiple computrs to support a specific set of services or application
• cluster - group of similar or identical computers that cooperate to provide services or execute a common application
• blade - circuit board that contains most of a server computer; a specialized cluster
• grid - group of dissimilar computer systems, connected by high speed network that cooperate to provide services or execute a common application
• the role of software is to translate the users request into machine instructions
• software types

  ap up ss

  • application programs
  • utility programs
  • system software
• application programs - stored set of instructions for responding to a specific information processing taks
• utility programs - contains instructions for performing general purpose tasks
• system software - implements utility functions needed by many application programs