HARDWARE: CPU & STORAGE How to Buy a Multimedia Computer System

Mathematical Backgrounds Data is stored in a computer using the Binary System. The Binary System has two numbers, 0 and 1 The Binary System is used because it is simple, cheap, and reliable to implement in a computer since 0 can represent a switch being off and 1 can represent a switch being on.

Mathematical Backgrounds (Continued) Two kinds of data are represented in a computer – numeric values and non-numeric values. Numeric values are numbers that are used for calculations Non-numeric values are either letters and other symbols or numbers that are not used for calculations such as phone numbers, SS numbers, etc.

Numeric Representation Numbers are represented in binary –Explain this on the board Fixed point or whole numbers are represented one way Floating point numbers or decimals are represented another way. Fortunately you don’t have to understand the details

Non-Numeric Representation Data is stored by codes. ASCII –American Standard Code for Information Interchange EBCDIC –Extended Binary Coded Decimal Interchange Code Unicode

ASCII See pager 178 for details

Parity Can be even, odd or neither Explain on board

Central Processing Unit The place where the computing is actually performed Consists of an arithmetic and logic unit or ALU and a Control Unit

ALU Performs the actual steps in running programs Contains special memory cells called registers

Control Unit The part of the CPU that tells the ALU what to do

Machine Cycle Fetch Decode Execute Store

Machine Language The language that the computer actually understands Pulse Patterns of zeros and ones.

Memory AKA Primary Storage Integrated circuits RAM ROM CMOS Cache

How the system does its work Explain on the Board

Storage AKA Secondary Storage The place where data and programs are kept on a “permanent” basis. Data and Programs are kept here when not in use

Memory vs. Storage Memory is also referred to as Primary Storage. Storage is also referred to as Secondary Storage. Stuff stays in memory while it is in use. Memory is volatile.

Fundamental Concepts Size of Storage –Bytes, kilobytes, megabytes, … Access Methods –Sequential –Direct Physical Devices Used –Disk (Fixed, floppy, removable), CDRom, DVD- ROM –Magnetic Tape -- cassette, open reel –Flash memory

How a Disk Drive Works Media Layout –Tracks –Sectors –Disk block –Cluster Size Logical Layout –Boot record –Directory –Allocation Table

Disk Drive Operation (cont) Heads Rotation Formatting Write Protection Interface –IDE –SCSI Disk Cache

Differences for CDRom, CDR, and CDRW No Tracks – spiral instead Laser Dyes

How a Tape Drive Works Sequential Used primarily for archival storage

How Flash Memory Works Just like regular memory except that it is not volatile

Storage Characteristics Capacity – how much it holds Access speed – how fast the data can be LOCATED Transfer Rate – how fast the data can be moved to memory Size – how big is the device Removability – can MEDIA be moved from one place to another – Can the DEVICE be moved conveniently Cost Read Write Erase – Which

Capacity How much data can the media hold. 720K up to 100GB is typical of current computers. My first hard disk cost $770 and had a capacity of 20mb. My current machine has a disk which I paid $300 for and has a capacity of 30,000 mb. I can go to a typical retailer such as Office Max and find a disk of about 40,000 mb for about $100 or less.

Capacity (continued) A CDRom can hold approximately 650mb of data A DVDRom can hold approximately 17000mb of data A floppy holds 720K, 1.44mb A removable disk holds 100mb or more (I have one that holds 2200mb and another that holds 120mb) Flash memory holds 8, 16, 32, 48, 64, up to 256mb

Access Speed Measured in milliseconds Based on rotational speed and head movement

Transfer Rate How fast the data moved from the disk to the buffer and or memory and or cache Currently the rate is about 15mb/sec typical with the fastest disks THEORETICALLY near 100mb/sec.

Read Write Erase Some media such as CDRom cannot have data added to it Some media such as CDR can have data added to it but it cannot be erased (WORM) “Most” media can be read, written and erased numerous times.

Compression A technique for removing redundant data from a data file in order to store it in a smaller space and therefore make it faster to transmit from one place to another Lossy –JPEG, MPEG, MP3,… “Lossless” –ZIP, ARC, others

Digital Manipulation of Pictures and Sound Entertainment Ethical and Legal Implication