LIS508 lecture 3: computer & input devices

Thomas Krichel2002-10-06

Admin news

• Grades for the quizzes will be made available at

• http://wotan.liu.edu/home/krichel/lis508w03a/grades/secret.html

• where secret is your word, transliterated into all lowercase, example– seCret secret– SecrEt secret

Literature

• Peter Norton “New inside the PC” chapter 1 and 5

• Ruth Maran and Paul Whitehead “Teach yourself computers visually”, chapter 1 and 3

• Hutchinson and Sawyer chapter 2• White, part 5

Hardware and Software

• Hardware is anything in the computer you can touch.

• Software are the instructions that make the computer do things.

• In early days, software was closely tied to hardware. It could only run on machines of a specific hardware and was useless on other machines.

structure

• general things about computers• looking at computer hardware• bus• input devices

– keyboard– mouse– other

Computers

• An old distinction is the following– A Mainframe is a computer that are used by

many people in an organization. They access it through terminals.

– A personal computer is a machine that is used by only one person at a time. In olden days it could only do one thing at a time.

• A PC is a special type of personal computer.

What is a PC

• The PC was first brought out by IBM in 1981– IBM published the design.– Processor chips supplied by Intel.– Software to run it was bought from Microsoft– Microsoft had the right to have other companies use

the operating system.• A PC is any computer that basically follows this

tradition.– Intel processor– Microsoft software

Basic parts of a PC• Display do not open• Input no need to open

– Keyboard – Mouse etc

• System Unit may be opened– Logic system– Display system– Storage system– Input output system– Communication system

Opening the system unit

• Voltages used in the PC are 3 to 12 V• Be aware of static electricity, touch first

unpainted part of case first• Keep power cable plugged in a grounded

socket• Never open sealed part of the power

supply

Logic system I

• Motherboard – green plastic sheet – with traces and slots – usually complying to a standard called “plug

and play”• Jumpers can set key features

– Jumper wires stick out of the motherboard– Can be shortened with jumpers– Do not change unless you have to

The logic system II

• CMOS or flash memory– Powered by battery – holds the Basic Input Output System (BIOS)

• Central Processing Unit (CPU), recognizable through its fan

• Cache memory for CPU• Main memory socket• The Bus (see later)

BIOS

• Is the software that makes the components of the PC work together

• When the computer boots it tells you how to “enter setup”

• There you can make changes to the BIOS setting

• The way that you do this is not standardized– It usually is a simple menu.– Be careful

Usual things to set in the BIOS

• Set the hardware clock • Set processor speed setting• Tell the machine what disks you have• Power management options• Automatic wake up• Boot sequence setting

The Bus

• Set of connections between devices in the system unit. Not very precisely defined

• Types of bus– Industry Standard Architecture ISA bus (16

bit), old– Peripheral Component Interconnect PCI bus

(32 bit)– Accelerated graphics port (AGP) bus, only for

graphics

The CPU

• Quality of CPU is a major component of the speed of the machine

• Speed of the CPU is measured in Hertz, as the number of instructions per second.

• Intel are the main manufacturer– Pentium– Celeron Processor

• but other manufacturers may be offering better quality/price.

The components on the bus

• The display system– Video card

• Storage system– Hard disk– Floppy disk– CD-rom– CD-R– CD-RW

Other components on the bus

• Modems, allow communication over a phone line– Internal modems with own serial device– It squeaks

• Network interfaces– network cards

Input/Output components

• Parallel port – Parallel because it can move a whole byte at a time – Mainly used for connection to a printer– Nowadays it can handle bidirectional traffic

• Serial port– One bit at a time -- Uses thin cable– Slow -- inexpensive

• Universal serial bus (USB) replaces those

Universal Serial Bus (USB)

• It is a new, rectangular port device• 4 wires

– 2 for power– 2 for communication

• USB has a hub/slave technology– One USB line can connect to a hub– The hub has several outgoing lines, that connect to

other devices• This is achieved by a complex set of software

Keys on a keyboard

• Typewriter keys• Function keys• Arrow keys• Editing keys• Numeric keypad• Alt and Control keys• Escape, windows key• Obsolete keys

Scholes layout

• Initial layout be Christopher Scholes around 1860.

• Early typewriters jammed when adjacent keys were typed to fast.

• Scholes design resulted from trying to avoid this occurrence.

• This resulted in the famous qwerty keyboard.

Dvorak keyboard

• An efficient keyboard for the English language, patented by August Dvorak, cousin of the composer.

• Result of efforts to study typewriting behavior.

• Studies in the US Navy suggest that the payback period would be 10 days from learning Dvorak.

• From my own experience, doubtful.

The mouse

• There are two-button and three button mice.

• Since MS uses two buttons, three button mice are a dying species.

• The third (middle) button can be emulated on two-button mice by pressing the left and the right button at the same time.

• Use of the mouse is best avoided!

The two buttons

• Primary button -- usually left• Secondary button – usually right • Actions in Microsoft windows

– Left click– Right click– Left double click (time adjustable)– Left drag and drop – Right drag and drop

Health risks

• Keyboard and mouse usage can cause serious injury.

• From my experience, they are often not be the lone cause.

• Others are – Stress– Bad posture

other devices

• Replacements for a mouse are– trackballs– touchpads– joysticks

• Pen-based devices– vary with respect to text recognition

text and code scanners

• bar-code readers• magnetic ink character recognition such as

on bank checks.• optical mark recognition• optical character recognition

– more general form of reading characters out of handwriting or print

– expensive and error-prone

image scanners

• most widely used digitization device• you can try to run OCR once you have the

image• resolution measured in dots per inch. dpi

– more dpi: crisper image– fewer dpi: smaller file

audio input

• Microphone with speech recognition software– This used to be mainly for those who can not

type– But the quality has improved, and maybe we

will use it for more general input.• Other analog to digital sound converters

– sound cards– MIDI board

Other devices

• sensors• biometric devices

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Thank you for your attention!