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

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

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

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

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

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

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 DecimalBinary Copyright © 2008 by Helene G. Kershner

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

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

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

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