Introduction to Computers From Chapters 1 & 2, Computers- Understanding Technology 1Bill Pegram - August 30, 2009.

Introduction to Computers

From Chapters 1 & 2, Computers- Understanding Technology

1Bill Pegram - August 30, 2009

What is a Computer

• Operates under control of a set of instructions, that is stored in its memory

• Accepts data from a user

• Manipulates the data according to the programmed instructions

• Produces the results

• Stores the results for future use

Bill Pegram - August 30, 2009 2

Special-Purpose vs. General- Purpose Computers

• Special-purpose, or embedded computers, perform a few specific actions whereas general purpose computers can perform a wide range of actions

• Examples of special purpose computers would include chips in digital thermometer, microwave oven, digital camera, car


Terminology

• Digital (0 vs. 1, on vs. off) vs. analog (pulses in continuous wave)

• Microcomputer or personal computer (intended to be operated by a single user)


Information Processing Cycle

• Input

• Processing

• Output

• Storage


Computer System Hardware Components

• Motherboard - Central Processing Unit (CPU) (Chapter 2) and Memory (Chapter 2)

• Input Devices (Chapter 2)

• Output Devices (Chapter 3)

• Storage Devices (Chapter 3)

• Communications Devices


Software

• System software (Chapter 4) - Operating system (e.g. Windows, MacIntosh)

• Utility software (e.g. file backup, virus protection)

• Application software (Chapter 5) – Office software, browsers, etc.

• Communications software


Categories of Computers (p. 23)

• Personal computers

• Handheld computers

• Workstation

• Midrange server

• Large server or mainframe computer

• Supercomputer


History of Computers Timeline

• Pages TI-A1-A14 following first chapter


Input Devices

• Keyboard – alphanumeric & special function (some at fast food restaurant but touch screens increasing used)

• Touch screen – ATMs, airport checkin counters, kiosks, restaurant cashier, grocery store self-service checkout (e.g. Giant, Harris Teeter), VA DMV Written Test for Driver’s license, Apple iPhone, Windows 7 (successor to Vista)

• Mouse• Trackball – plastic sphere resting on rollers, often used

in laptop computers• Touchpads – you move the pointer by sliding your

finger across the surface of the pad


Input Devices

• Operating systems such as Windows and Macintosh employ a graphical user interface (GUI – pronounced gooey) in which the user issues command by using a mouse to make selections

• With DOS (the previous operating system for IBM-compatible computers), users issued commands through typing on a keyboard


Mouse Technology

• Mouse has used a rubber-coated ball on the bottom of the mouse; movement of the mouse on a surface results in rotation of the ball which is recorded by sensors in the mouse

• An optical mouse uses a light sensor instead of a ball to track movement


Input Devices (cont.)

• Microphone (audio input)

• Joystick – computer games

• Graphics tablet and pen

• Optical scanner

• Bar code readers, magnetic card readers

• Digital cameras


Input Devices (cont.)

• Digital video cameras – including retinal and thumb print scanners (e.g. preferred travellers at airports, thumb print scanners at tanning salons to prevent multiple visits within 24 hours)

• Nintendo Wii Remote and Platform


Computer Representation of Data

• Bit (either 0 or 1)

• Byte - 8 bits

• ASCII (7 bit encoding) – PC’s

• EBCDIC (8 bit encoding) – large computers

• Unicode (16 bit) – used in newer operating systems such as Windows Vista and Macintosh OS X


System Unit

• Power supply – converts from AC into DC and fan

• Bay or Storage bay – site where storage device can be installed

• Motherboard – thin sheet which has a number of components connected to it (see next slide)


Motherboard

– CPU– System clock and battery– Slots for RAM chips– One or more read-only memory chips– Expansion slots– Ports for connecting input and output devices– Buses, which allow communication between

components in the computer


Bays

• A bay is a site where a device such as a floppy disk drive or hard drive is installed

• An internal bay is concealed entirely within the computer case

• An exposed bay has an opening to the outside of a computer case


Bays (cont.)

• The availability of empty bays used to be an important constraint on expanding the capabilities of a computer; much less important now due to the ability to connect external devices through USB ports (see later)


Central Processing Unit

• Control unit – interprets program instructions and initiates action to carry them out – fetch and decode portion of machine or instruction cycle

• Arithmetic/logic unit (ALU) – execute part of cycle

• Registers – temporary storage locations that can be accessed much faster than locations outside of the CPU; instruction registers, data registers, storage registers


CPU (cont.)

• System clock – generates pulses which synchronize activity within computer

• Clock speed is measured in hertz (pulses per second) – megahertz (MHz) (1 million/sec) and gigahertz (GHz) (1 billion/second) – chart p. 73

• One clock cycle equal to 2 clock ticks• Coprocessors – math, graphics,

cryptographic21Bill Pegram - August 30, 2009

Key Advances in Microprocessors

• Reduced instruction set computing (RISC)

• Pipelining – computer can begin executing another instruction as soon as previous instruction reaches next phase of machine cycle

• Closer circuits

• Better materials

• Parallel processing


Key Advances in Microprocessors (cont.)

• Multithreading and hyperthreading – allows parallel processing

• Dual-core and multi-core processors


Memory

• Random access memory (RAM) – each memory location has its own address so CPU can go directly to the instructions and data it needs

• Random access memory is reusable (new data or instructions can replace what was formerly there)

• Random access memory is volatile memory; only retains information while power is on


Cache Memory

• Cache memory contains data and instructions recently used by processor; when CPU looks for data or instructions, it first looks in the cache

• Because there is often repeat use of data or instructions, this decreases time required to get the information

• A browser cache for images speeds up web surfing


Read-only Memory (ROM)

• ROM contains instructions or data permanently there; does not depend on maintaining continuous power

• ROM contains BIOS (basic input/output system) program which is the program that boots or starts the computer when it is turned on


Flash Memory

• Nonvolatile memory that can be erased and reused

• Used in many handheld computers and devices including flash drives (thumbnail drives) – significant increase in size and decrease in cost in last couple years


Expansion and Ports

• Expansion boards – sound, video, graphics, modem, etc.

• Ports – external plug-in slot – serial or communications (COM) (one bit at a time)– Parallel (LPT)– traditionally used to connect printer– Video – connect monitor– USB (Universal Serial Bus) – can be used to connect

many type of devices


Buses

• A bus is a pathway within a computer along which bits are transmitted

• Bus width refers to number of bits that can be transmitted at one time; e.g. 32-bit bus

• Expansion bus – interacts with RAM and low-speed devices

• Local bus – high speed peripherals and connects directly to CPU


Introduction to Computers From Chapters 1 & 2, Computers- Understanding Technology 1Bill Pegram - August 30, 2009.

Documents

car bill pegram

input devices chapter

embedded computers

categories of computers

future use bill pegram

general purpose computers

mouse technology mouse

output devices chapter