CCC101 chapter 1

• Computer program


  A set of instructions for a computer to follow
• Computer software


  The collection of programs used by a computer
• Three main classes of computers

  • PC
  • Workstation
  • Mainframe
• PCs


  • Relatively small used by one person at a time
• Workstation


  • Larger and more powerful than a PC
• Mainframe


  • Still larger
  • Requires support staff
  • Shared by multiple users
• Network


  A number of computers connected to share resources
• What networks allow sharing of

  • Printers and other devices
  • Information
• Five main components of a computer

  • Input devices
  • Output devices
  • Processor (CPU)
  • Main memory
  • Secondary memory
• Input devices


  Allows communication to the computer
• Output devices


  Allows communication to the user
• Processor (CPU)


  Main component that follows program instructions
• Main memory


  Memory locations containing the running program
• Secondary memory


  Permanent record of data often on a disk
• Binary Digit or Bit

  A digit that can only be zero or one
• Byte


  Each memory location has eight bits

  
• Address


  Number that identifies a memory location
• Some data is too large for a single byte, most integers and real numbers are too large
• Address refers to the first byte, next few consecutive bytes can store the additional bits for larger data
• The computer knows the meaning of 01000001 based on the current instruction
• Programmers rarely need to be concerned with the interpretation of 01000001
• Secondary memory


  Stores instructions and data between sessions
• File


  Stores data or instructions in secondary memory
• Types of secondary memory

  • Hard disk
  • Floppy disk
  • Compact disk
• Hard disk


  • Fast
  • Fixed in the computer and not normally removed
• Floppy disk


  • Slow
  • Easily shared with other computers
• Compact disk


  • Slower than hard disks
  • Easily shared with other computers
  • Can be read only or re-writable
• Random Access (RAM)


  Computer can directly access any memory location
• Sequential Access


  Data is generally found by searching through other items first
• Processor (CPU)


  Follows program instructions
• Typical capabilities of CPU

  • Add
  • Subtract
  • Multiply
  • Divide
  • Move data from location to location
• Operating system

  • Allows us to communicate with the computer
  • Allocates the computer's resources
  • Responds to user requests to run other programs
• Common operating systems


  • UNIX
  • Linux
  • DOS
  • Windows
  • Macintosh
  • VMS
• Computer input consists of a program and some data
• High-level languages

  • Resemble human languages
  • Are designed to be easy to read and write
  • Use more complicated instructions than the CPU can follow
  • Must be translated to zeros and ones for the CPU to execute a program
• Examples of high-level languages

  • C
  • C++
  • Java
  • Pascal
  • Visual Basic
  • FORTRAN
  • COBOL
  • Lisp
  • Scheme
  • Ada
• Assembly language


  Must be translated to machine language (zeros and ones) for the CPU to execute
• Source code


  The original program in a high level language
• Object code

  The translated version in machine language
• Compiler


  Translates high-level language to machine language