Hardware: Input, Processing, and Output Devices Chapter 3

Chapter Topics Computer system components The power, speed, and capacity of processing and main memory devices. Access methods, capacity and portability of secondary storage devices. Input & output devices The popular classes of computer systems

Hardware: Typical System Printer (output) Monitor (output) Speakers (output) Mouse (input) Keyboard (input) System unit (processing and secondary storage)

Computer Hardware CPU Memory System Unit Input Devices Storage Output Peripherals “Ports” “Motherboard” “Expansion Slots”

On the Motherboard A “motherboard” CPU A RAM chip A “firewire” card Pins to attach to The motherboard Expansion slots

CPU Fetch Decode Execute Write-back Memory Registers ALU Control Unit

CPU Control Unit Arithmetic/logic Unit (ALU) Registers Maintains order Controls CPU activity Directs sequence of operations Arithmetic/logic Unit (ALU) Manipulates data Performs arithmetic computations Performs logical operations Registers Temporary storage areas for instructions or data offer the advantage of speed work under the direction of the control unit to accept, hold, and transfer instructions or data

Machine Cycle Fetch Decode Write-back Execute Instruction Cycle Execution Cycle

Machine Cycle Time Measures Microseconds (1 millionth) Nanoseconds (1 billionth) Picoseconds (1 trillionth) MIPS (Millions of Instructions Processed per Second)

How fast is a Nanosecond? If one nanosecond is.. One mile One person One minute One square mile Then one second is equivalent to … 2000 trips to the moon and back Population of China and the U.S. 1900 years 17 times the land are of the world

Data Bus Fetch Decode Execute Write-back “Word sizes” 8 bits 16 bits

Processing Characteristics Clock speed: electronic pulses affecting machine cycle time Hertz: one cycle (pulse) per second Megahertz (MHz): millions of cycles per second Microcode: internal, predefined elementary operations in a CPU

Microcode Instruction Sets Complex instruction set computing: CPU contains many microcode instructions Reduced instruction set computing (RISC): Minimal set of microcode instructions Very Long Instruction Word (VLIW): Each microcode instruction is longer and does more.

Multiprocessing More than one CPU is present Tasks are divided among CPUs in true “parallel processing” Parallel processing uses multiple processors to execute instructions in concert.

Parallel Processing Control CPU Combined Results

Physical Characteristics of the CPU Digital circuits on chips Electrical current flows through silicon Moore’s Law states that transistor density of chips will double every 18 months

Memory Characteristics and Functions

Memories Random Access Memory (RAM) ROM CPU Secondary Primary Cache System Bus External Storage Devices Expansion slots I/O Bus ROM

ROM Chip and BIOS ROM stands for Read Only Memory ROM is a non-volatile memory on a chip The ROM chip contains Basic input/output system BIOS The BIOS has the instructions necessary to start up your computer

RAM RAM stands for Random Access Memory RAM is a volatile memory on a chip RAM chips store information in “addresses” that can be accessed directly and quickly

Storage Media Storage devices retain data when power is switched off Storage devices are slower than memory devices like RAM

Memory Versus Storage Memory Storage A temporary holding place for data and instructions Consists of one or more chips on the motherboard Sometimes called primary storage Storage The media on which data, instructions, and information are kept, as well as the devices that record and retrieve these items Storage also called secondary storage, auxiliary storage, permanent storage, or mass storage Storage is nonvolatile

Managing Memory Remember the “Machine Cycle?” Page is Decoding and “swapped in” Decoding and Execution Page is “swapped out”

Starting Up BIOS read 2. OS “kernel,” or from ROM supervisor program becomes memory resident. 3. CPU reads and executes instructions

Storage Capacity Storage Term Number of bytes Abbreviation The number of bytes (characters) a storage medium can hold Manufacturers use many terms to define the capacity of storage media Kilobyte KB 1 thousand Megabyte MB 1 million Gigabyte GB 1 billion Terabyte TB 1 trillion Petabyte PB 1 quadrillion

Data Representation A computer circuit represents the 0 or the 1 electronically by the presence or absence of an electronic charge. Binary Digit (Bit): Electronic State 1 On 0 Off Binary system: two unique digits, 0 and 1 Bit: the smallest unit of data the computer can represent A byte: a group of 8 bits: represents a single character in the computer

Bits and Bytes Byte Eight bits Kilobyte - 1 thousand bytes Megabyte - 1 million bytes Gigabyte - 1 billion bytes Terabyte - 1 trillion bytes

Coding Schemes A byte provides enough different combinations of 0s and 1s to represent 256 individual characters. A coding scheme: the defined combinations of 0s and 1s that represent characters by patterns ASCII(The American Standard Code for Information Interchange) ASCII represents 0-9, upper and lower case A-Z, and English language punctuation in byte code EBCDIC (The Extended Binary Coded Decimal Interchange Code) Unicode

Data Storage Hierarchy DOG….. CAT…. FOX…. File Record DOG, FOUR LEGS, TWO EARS Field DOG Character (byte) D O G Bits 01000100 01001111 01000111

Storage Modes Direct(Random) Access Sequential records can be retrieved in any order Faster (nanoseconds) Usually more expensive Sequential records must be retrieved in order Slower (milliseconds) Less expensive The dog barked. T H E D O G . Th bar d og k ed e

Sequential access versus Direct access Method used for floppy disks, hard disks, and compact discs Also called random access You can locate a particular data item or file immediately, without having to move consecutively through items stored in front of the desired data item or file Faster Used as the primary method of storage Sequential access Method used for tape Reading and writing data consecutively You must forward or rewind the tape to a specific point to access a specific piece of data Much slower Utilized most often for long-term storage and backup

Storage Technologies Magnetic Optical Read/write head uses electrical impulses to create or interpret patterns of magnetic impulses Floppy disks Hard disks Tape Optical Laser beam creates or reads non-reflective pits and reflective land areas CDs DVDs Ancient DecTape systems

Disks Read/Write Head Sector Cluster

Access time cost less expensive more expensive speed faster slower Memory (RAM) The amount of time it takes the device to locate an item on a disk Defines the speed of a disk storage device Hard Disk Compact Disc Floppy Disk Tape

CD-R & CD-RW CD-R (compact disc-recordable) You write on the CD-R using a CD recorder or a CD-R drive and special software The CD-R drive can read and write both audio CDs and standard CD-ROMs You cannot erase the disc’s contents Most CD-ROM drives can read a CD-R CD-RW (compact disc-rewritable) An erasable disc you can write on multiple times You must have CD-RW software and a CD-RW drive

DVD-ROM (digital video disc-ROM) An extremely high capacity compact disc capable of storing from 4.7 GB to 17 GB You must have a DVD-ROM drive or DVD player to read a DVD-ROM Looks just like a CD-ROM but data, instructions, and information is stored in a slightly different manner to achieve a higher storage capacity

Magnetic Tapes A magnetically coated ribbon of plastic capable of storing large amounts of data and information at a low cost A tape drive reads from and writes data and information on a tape Older computers used reel-to-reel tape drives A tape cartridge is a small, rectangular, plastic housing for tape used in today’s tape drives Used by business and home users to backup personal computer hard disks Both external and internal tape units for personal computers Larger computers use tape cartridges mounted in a separate cabinet called a tape library

Storage techniques used in an enterprise system Storage area network (SAN): A high-speed network that connects storage devices Tape library: A high-capacity tape system that works with multiple tape cartridges for storing backups of data, information, and instructions RAID system: Ensures that data is not lost if one drive fails Server: Stores data, information, and instructions need by users on the network CD-ROM jukebox: Holds hundreds of CD-ROMs that can contain application programs and data. Also called a CD-ROM server Internet backup: Stores data, information, and instructions on the Web

RAID Redundant array of independent disks A type of hard disk system that connects several smaller disks into a single unit that acts like a single large hard disk More reliable than a traditional disk system but quite expensive RAID duplicates data, instructions, and information to improve data reliability

How does RAID work? Level 1, called mirroring, has one backup disk for each disk Levels beyond level 1 use a technique called striping, which splits data, instructions, and information across multiple disks in the array Mirroring (RAID Level 1) Striping

Additional Devices and Media Memory Cards A thin, credit card-sized device Fits into a PC Card slot on a notebook other personal computer Different types and sizes add storage, additional memory, communications, and sound capabilities to a computer Three types of PC Card Advantage of a PC Card for storage is portability between systems Flash memory Also called flash ROM or flash RAM Nonvolatile memory that can be erased electronically and reprogrammed Stores data and programs on many handheld computers and devices Flash memory cards store flash memory on removable devices instead of chips

Input and Output Device Driver software Interrupts

Input devices What is input? Types of input Any data or instructions you enter into the memory of the computer Users can input data and instructions in a variety of ways Types of input Data: A collection of raw unprocessed facts, figures, and symbols Instructions: Programs, Commands, User responses

Data Data can be human or machine readable Data entry converts human readable data into machine-readable form Data input transfers machine-readable data into the system Source data automation

Input Devices Personal computer input devices Keyboard Mouse Voice-recognition devices Digital cameras Terminals

Input Devices Scanning devices Optical data readers Bar code scanners MICR devices POS (point-of-sale) devices Pen input devices Light pens Touch screens

Output Devices Monitors Printers Plotters Cathode Ray Tubes (CRTs) Liquid Crystal Displays (LCDs) Active matrix Passive matrix Printers Plotters Computer Output Microform (COM) Music Devices

What is a CRT monitor? Contains a cathode ray tube (CRT), a large sealed, glass screen The screen is coated with tiny dots of phosphor material A pixel, or picture element, is a single point in an electronic image Three dots (red, blue, and green) combine to make up each pixel cathode ray tube screen CRT monitor

What is a liquid crystal display (LCD) monitor? A type of flat-panel display Uses liquid crystals between two sheets of material to present information on a screen An electric current passes through the crystals which creates the images on the screen

What is display resolution? Describes the sharpness and clearness of an image Resolution of a display device stated as dots, or pixels 800 x 600 typically the standard 800 horizontal pixels 600 vertical pixels 1280 x 1024 maximum resolution of most monitors Total of 480,000 pixels on screen 2048 x 1536 maximum for high-end monitors

What is a video card? Converts digital output from the computer into an analog video signal Sends the signal through a cable to the monitor Controls how the display device produces the picture Also called a graphics card or video adapter

How does video travel from the processor to a CRT monitor? Step 1: The processor sends digital video data to the video card. Step 2: The video card’s digital-to-analog converter (DAC) converts the digital video data to an analog signal. Step 3: The analog signal is sent through a cable to the CRT monitor. Step 4: The CRT monitor separates the analog signal into red, green, and blue signals. Step 5: Electron guns fire the three color signals to the front of the CRT. Step 6: An image displays on the screen when the electrons hit phosphor dots on the back of the screen.

What is bit depth? 28 = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256 colors 8-bit video card (8-bit color) Uses 8 bits to store information about each pixel Can display 256 different colors 28 = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256 colors What is bit depth? The number of bits a video card uses to store information about each pixel Also called the color depth Determines the number of colors a video card can display The greater the number of bits, the better the resulting image 24-bit video card Uses 24 bits to store information about each pixel Can display 16.7 million colors 224 = 16.7 million colors

What are various video standards? The Video Electronics Standards Association (VESA) develops video standards

Computer System Types Network computer Personal computer Workstation Midrange computer Mainframe computer Supercomputer

Selecting and Upgrading Computer Systems Computer system architecture: the configuration of a computer system’s hardware components