Welcome%20to%20Computing

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Welcome to Computing

• Presentation slides modified by M. A. Papalaskari
  from Java Software Solutions Foundations of
  Program Design (3rd ed.) by John Lewis and
  William Loftus

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Overview

• History of computing
• Information representation
• Computer hardware
• Computer software

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History of Computers
Mechanization of arithmetic
Abacus (China 2400 bc) Stonehenge (1900-1600 bc) Napier's bones (c. 1600, a precursor of the slide rule) Pascal's adder (1642) Leibniz's calculator (1670s) Babbage's Difference engine (1800s) modern calculators
Automatic control of computation
Jacquard loom (1801) Babbage's Analytical engine (1822) Holerith's census machine (1890)
Modern Computer
Stored program and the fetch/decode/execute cycle (John von Neumann, 1945) ENIAC - first fully electronic digital computer (Eckert and Mauchley, 1946)
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Hardware and Software

• Hardware
• the physical, tangible parts of a computer
• keyboard, monitor, disks, wires, chips, etc.
• Software
• programs and data
• a program is a series of instructions
• A computer requires both hardware and software
• Each is essentially useless without the other

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CPU and Main Memory
Chip that executes program commands Intel
Pentium 4 or Sun ultraSPARC III Processor
Central Processing Unit
Primary storage area for programs and data that
are in active use Synonymous with RAM
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Secondary Memory Devices
Information is moved between main memory and
secondary memory as needed
Secondary memory devices provide long-term storage
Central Processing Unit
Hard disks Floppy disks ZIP disks Writable
CDs Tapes
Main Memory
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Input / Output Devices
I/O devices facilitate user interaction
Central Processing Unit
Monitor screen Keyboard Mouse Joystick Bar code
scanner Touch screen
Main Memory
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Analog vs. Digital

• There are two basic ways to store and manage
  data
• Analog
• continuous, in direct proportion to the data
  represented
• music on a record album - a needle rides on
  ridges in the grooves that are directly
  proportional to the voltages sent to the speaker
• Digital
• the information is broken down into pieces, and
  each piece is represented separately
• music on a compact disc - the disc stores numbers
  representing specific voltage levels sampled at
  specific times

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Digital Information

• Computers store all information digitally
• numbers
• text
• graphics and images
• video
• audio
• program instructions
• In some way, all information is digitized -
  broken down into pieces and represented as numbers

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Representing Text Digitally

• For example, every character is stored as a
  number, including spaces, digits, and punctuation
• Corresponding upper and lower case letters are
  separate characters

H i , H e a t h e r .
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Representing images

• A digitized image consists of pixels (picture
  elements)
• Black and white images can be stored using one
  bit per pixel (1 white and 0 black)
• There are several techniques for representing
  colors
• Often a color is represented as a mixture of the
  three additive primary colors Red, Green, and
  Blue
• In many applications each color is represented by
  three numbers between 0 and 255 that collectively
  are called an RGB value

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The Central Processing Unit

• A CPU is on a chip called a microprocessor
• It continuously follows the fetch-decode-execute
  cycle

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The Central Processing Unit

• The CPU contains

Performs calculations and makes decisions
Arithmetic / Logic Unit
Coordinates processing steps
Control Unit
Small storage areas
Registers
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The Central Processing Unit

• The speed of a CPU is controlled by the system
  clock
• The system clock generates an electronic pulse at
  regular intervals
• The pulses coordinate the activities of the CPU
• The speed is measured in megahertz (MHz)

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Software Categories

• Operating System
• controls all machine activities
• provides the user interface to the computer
• manages resources such as the CPU and memory
• Windows XP, Windows 2000, Unix, Linux, Mac OS
• Application program
• generic term for any other kind of software
• word processors, missile control systems, games
• Most operating systems and application programs
  have a graphical user interface (GUI)