1. Slide 7-1 Chapter 7 Computer Components and Options Introduction to Information Systems Judith C. Simon

2. Slide 7-2 "Copyright © 2001 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without the express written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein."

3. Slide 7-3 Chapter 7 Major Topics ä Input and output ä Secondary storage ä Processing

4. Slide 7-4 Input ä Input: collecting raw data to be processed ä Forms of input include: ä Keyboard (most widely used input device) ä Pointing devices, such as mouse, trackball, touch pad, touch-sensitive screen, pen ä Scanners, including desktop systems with OCR programs, POS terminals, MICR ä Voice recognition

5. Slide 7-5 Output ä Output: converting computer data into a form usable by humans ä Forms of output include: ä screens (monitors) ä printers ä voice (audio)

6. Slide 7-6 Input and Output Similarities ä Some hardware may be the same for both operations, e.g., travel path of data entering and leaving the computer system is the same ä Storage devices can serve as source of data to be processed as well as final destination of data ä Transmission of data over long distances may involve modem and telephone lines for output of data from one computer and input of data to another computer

7. Slide 7-7 Monitor Considerations ä Screen size, such as 17” ä Dot pitch (dp); spacing between dots, such as.28 mm; smaller dp number is better ä Screen resolution (number of picture elements - “pixels”); example: 1024 x 768 ä Refresh rate, referring to the number of times per second that the image is redrawn ä Video card support, which is memory available to support higher resolutions

8. Slide 7-8 Printer Considerations ä Laser vs. ink jet (laser usually is higher quality and faster printing but more expensive; ink jet with color cartridges is not very expensive and becoming widely used when color is needed) ä Output quality, e.g., dots per inch (dpi) and pages per minute (ppm) ä Ease of use ä Compatibility with software in use ä Other capabilities, such as paper sizes, fonts, etc.

9. Slide 7-9 Encoding Systems ä Binary system of 0s and 1s is used (each 0 or 1 is referred to as a bit, a term derived from binary digit) ä Groups of bits representing characters are called bytes ä Various powers of 2 are used to represent capabilities, such as 2 8, which has 256 combinations of 1s and 0s; 2 10, with 1,024 combinations; 2 16, with 65,536 combinations, etc. ä EBCDIC and ASCII are two encoding systems that have been widely used; ASCII is now the standard encoding system for microcomputers

10. Slide 7-10 Binary System Concept ä Binary system: ä Two options, designated as 1 and 0 ä Examples ä Onvs.Off ä Conductingvs.Nonconducting ä Positivevs.Negative

11. Slide 7-11 Differences in Storage Sizes Gigabyte >1 billion bytes Megabyte >1 million bytes Kilobyte >1 thousand bytes

12. Slide 7-12 Tape Storage Media ä Reel-to-reel magnetic tape: used for many years in large systems; inexpensive method of providing backup data; often designed with 9 parallel rows (tracks) with 8 tracks for the bits of a character and the 9th track for a parity bit ä Magnetic cartridge: often used for microcomputer backup systems, as cost per byte is lower than on disk media

13. Slide 7-13 Magnetic Disk Storage Media ä Disks are direct access storage devices (DASD), because each storage position has a unique address that can be accessed directly instead of limited to the sequential design of magnetic tape media ä Disks have tracks that are subdivided into “sectors”; the tracks and sectors are part of the data’s address used for access ä Two forms of magnetic disk are floppy disks and hard disks

14. Slide 7-14 Floppy Disks ä Most microcomputers today have a 3 1/2” floppy disk drive and may also have a Zip disk drive ä Disk drives have read/write heads (also used with magnetic tape systems), which are on access arms that move over a disk ä Access time: how long it takes for a seek operation (reaching the appropriate track) and a search operation (reaching the appropriate position on the track); then data is transferred to memory

15. Slide 7-15 Hard Disks ä Use of a disk drive with one or more metal disks, usually built into the computer hardware and tightly sealed ä Operates similarly to a floppy disk drive, but hard disk drive can rotate faster ä May include multiple disks arranged as a disk pack, in which disks rotate together with access arms in between disks; a particular track location on all disks is called a cylinder and is used as part of an address of data stored on a disk

16. Slide 7-16 Optical Disk Storage Media ä Uses laser technology ä Has a longer shelf life than magnetic media ä Cost of storage is higher than for magnetic media ä Can be used for permanent storage of data, in which what is stored is never changed, and also for data that can be erased so that the disk can be reused ä Used extensively for storage of images

17. Slide 7-17 “Write-Once” Disks ä WORM technology: acronym for “write once, read many”; data that is stored cannot be erased but can be read as often as desired ä Disk may continue to be used for data storage until it is full, although existing data cannot be changed ä Permanence of storage has allowed data stored in this way to be used as legal evidence and for other permanent records ä CD-ROM is written to only once, usually all at one time, rather than being able to add data later

18. Slide 7-18 Rewritable Disks ä Typically use a combination of optical and magnetic technologies, sometimes referred to as magneto-optical (MO) technology ä Data is stored magnetically, with a laser beam used for changes to the data ä Cost is higher than for magnetic disks but have faster access times and data transfer rates

19. Slide 7-19 Storage Media Comparison ä Magnetic tape ä Widely used for backup copies, in which sequential arrangement is acceptable ä Magnetic disk ä Useful for day-to-day activities requiring direct access ä Optical disk ä Useful when storage of photos and other images is required

20. Slide 7-20 Computer Processing Overview ä Processing: activities involved in converting data (input) into a desired output form ä Two parts of the computer system primarily involved in processing are: (1) central processing unit (CPU), where actual processing occurs, and (2) primary memory (or “memory”), where needed data and programs are stored temporarily

21. Slide 7-21 Conceptual View of Processing CPU Primary Memory Other System Components Data Programs

22. Slide 7-22 General Procedures in Processing Data ä Data is read from secondary storage into primary memory for processing. Results are then displayed on the computer screen. Pri ma ry M em or y Secondary Storage Result Action Primary Memor y Secondary Storage

23. Slide 7-23 Primary Memory ä Primary memory temporarily stores instructions, data, and results; referred to as “volatile”; contents of memory may be lost if the power goes off ä Contents are replaced by other data brought in to the same location, a write process that is referred to as “destructive”; accessing data but not changing it is a read process, which is “nondestructive”

24. Slide 7-24 Read-only Memory (ROM) vs. Random Access Memory (RAM) ä ROM contains permanent instructions that are not erased when the power is off, so it is “nonvolatile”, while RAM is the area used for the temporary internal storage of instructions and data that is “volatile” ä Forms of ROM include PROM, EPROM, and EEPROM ä Forms of RAM include SRAM and DRAM ä RAM takes advantage of cache, additional temporary internal storage areas that help speed up the processing

25. Slide 7-25 RAM versus ROM ä Random-Access Memory (RAM) ä Working area for various activities ä Temporary holding place for data/programs ä Contents retained only when computer is on ä Read-Only Memory (ROM) ä Location of startup procedures ä Holding place for all permanent internal instructions ä Contents retained when computer is on or off

26. Slide 7-26 Central Processing Unit (CPU) ä Two main components that must work with the primary memory in order for processing to occur in the CPU: (1) control unit, which interprets instructions and manages the sequence of operations, such as sending of data in and out during processing (2) arithmetic-logic unit, where arithmetic (mathematical) and logical (comparison) operations are actually performed

27. Slide 7-27 Machine Cycle ä Sequence of events for CPU to interpret and execute a program instruction ä Instruction cycle: part of the machine cycle during which an instruction is obtained and interpreted ä Execution cycle: part of the machine cycle during which operations are performed based on results of instruction cycle ä MIPS: millions of instructions per second; used as a computer speed comparison measure for many larger systems

28. Slide 7-28 Parallel Processing ä Multiple processors used in a design allowing each processor to operate independently, usually without sharing memory once a program is subdivided (traditional multiprocessing design involves sharing of memory, which limits the overall capabilities possible with that system) ä Massively parallel processing: at least 1,000 processors operating in parallel

29. Slide 7-29 Microprocessors - Speed Factors ä Clock speed (number of electronic pulses produced each second) ä Word size (number of bits that can be processed at one time) ä Bus width (number of bits that can travel at one time) ä Memory capabilities (how much data and instructions can be available at a time) ä Cache size and type (some cache is closer to the processor and thus has faster access)

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