1. What’s a Computer? Analog, Digital does it matter?
Technically there are two categories of computers, analog or digital.
Designs reflect two different ways to look at or analyze the world.
Copyright © 2008 by Helene G. Kershner

2. What’s a Computer? Analog, Digital does it matter?
Analog device – operates with measurements that are continuous such a voltage, temperature and rotation.
Speedometer in your car
Traditional thermometer
Classic clock
Analog computer uses analog measurements in it’s calculations
Very fast
Somewhat inaccurate
Difficult to replicate results, can you spin a wheel at exactly the same rate twice in a row?
Copyright © 2008 by Helene G. Kershner

3. What’s a Computer? Analog, Digital does it matter?
Digital Computer –
Information is represented by counting
This is what we think of as a computer.
All information used by the machine is one of two states ON (1) or Off (0).
Change from a dollar
Number of students registered in CSE 111
Tuition in dollars
Highly flexible
Easy to replicate
Copyright © 2008 by Helene G. Kershner

4. What’s a Computer? Analog, Digital does it matter?
Moving from Analog to Digital
Digital Age
Clock
Hands moving in a circle  digits on a screen
Telephone
10 digits in a circle, distance from beginning was used to represent the digit  push a button
Voice as a sound wave  voice as a pattern of pulses
Television and Movies
Pictures as a series of light waves  pictures as a pattern of dots (pixels).
It is all about speed and ability to replicate results
Copyright © 2008 by Helene G. Kershner

5. What’s a Computer? The Binary Machine
Computers “speak” a very simple language
Two digits – 0 and 1
Don’t really understand the data or instructions they are given
Know how to “follow” them -- circuit path
The 1 state, current is present -- ON
The 0 state, current is absent – OFF
Binary -- The entire language of mathematics can be converted into a system that just uses 0s and 1s.
Copyright © 2008 by Helene G. Kershner

6. What’s a Computer? The Binary Machine
Computers use Binary
(0,1)
Base 2
People do not – we use Decimal
(0,1,2,3,4,5,6,7,8,9)
Base 10
Perhaps this is because we have 10 finger and 10 toes
Modern computers take in decimal number and letters
Translate them into 0s and 1s
Do whatever they do – “Magic”
Give us the results in a way human understand
Copyright © 2008 by Helene G. Kershner

7. What’s a Computer? The Binary Machine
In decimal every number is represented as the digits 0-9
In binary every number is represented as the digits 0-1
Decimal to Binary conversion
Decimal Binary
Copyright © 2008 by Helene G. Kershner

8. What’s a Computer? The Binary Machine
For people in the know –
Copyright © 2008 by Helene G. Kershner

9. What’s a Computer? The Binary Machine
BIT for Binary Digit -- each 0 or 1 in the binary system
Single bit is not overly useful
BYTE – a group of bits (usually 8)
Each byte represents one character of data
Numbers, letters, special characters (%, $, # etc.)
Letter, numbers and symbols are the form we use to represent information.
WORD – the number of bits that can be processed at one time by the central processing unit (the “brain”) of the computer.
Early computers – Apple II – 8 bit Words
Modern machines – can process up to 64 bits/word
Copyright © 2008 by Helene G. Kershner

10. What’s a Computer? The Binary Machine
Computers are described by amount of processing memory they contain
Usually described in terms of bytes (K ~ 1000 bytes)
Megabyte or megs [MB]= ~1000K or ~1 million bytes
Gigabyte or gigs [GB] = ~1000MB or ~1 billion bytes
Terabyte = ~1000GB or ~1 trillion bytes
The notation has gained common usage
Earn 100K
House is priced at 450K
Copyright © 2008 by Helene G. Kershner

11. What’s a computer? Basic parts
Input & Output
Central Processing Unit
&
Arithmetic & Logic Unit
Input
Brains
Memory
Input & Output
Output
computer.howstuffworks.com/cd.htm, staples.com, dell.com
Copyright © 2008 by Helene G. Kershner