Chapter 3, 4 and 5

Computer Storage and MemoryComputer Storage and Memory

Albert Kalim

Memory: RAMMemory: RAM

RAM (random access memory) is the computer’s main memory and is used to temporarily storage programs and data with which it is working.

RAM is volatile (erased when the power to the PC goes off).

RAM comes in a variety of types, speeds, and size. Types of RAM include:

DRAMSRAM

SDRAM

DDR SDRAMRDRAM

DDR-II SDRAM

Memory: Other TypesMemory: Other Types

Cache memory—fast memory chips located on or close to the CPU chip (L1, L2, and L3).

Registers—high speed memory built into the CPU.

ROM (read-only memory)—non-volatile chips inside which data or programs are stored.

Flash memory—non-volatile memory that can be erased and reused. Used both within the PC and for portable storage media (e.g digital cameras).

Properties of Storage Systems: Properties of Storage Systems: Storage Devices and MediaStorage Devices and Media

Involve two physical parts: a storage device and a storage medium.

Can be internal (located inside the system unit), or external (located outside the system unit).

Storage devices are identified by names and/or letters (e.g. “C” for first hard drive).

Properties of Storage Systems: Properties of Storage Systems: Non-Volatility Non-Volatility

Storage media are non-volatile:

– When power to the device is shut off, data stored on the medium remains.

– This is in contrast to most types of memory, which are volatile.

Properties of Storage Systems: Properties of Storage Systems: Removable vs. Fixed MediaRemovable vs. Fixed Media

Fixed media: typically faster and less expensive.

Removable media: unlimited capacity and can be easily transported and secured.

Properties of Storage Systems: Properties of Storage Systems: Random vs. Sequential AccessRandom vs. Sequential Access

Random access ( direct access ): data can be retrieved in any order, independent of its physical location (most types of storage media).

Sequential access: data can be retrieved only in the same sequence in which it is physically stored (magnetic tape).

Properties of Storage Systems: Properties of Storage Systems: Logical vs. Physical Logical vs. Physical RepresentationRepresentationLogical file representation refers to the

user’s view of the way data is stored (filename, folders, etc.).

Physical file representation is the actual physical way the data is stored on the storage media as viewed by the computer.

Magnetic Disk SystemsMagnetic Disk Systems

Magnetic disks are the most widely used storage medium in computers today.

Data is stored by magnetizing particles on the storage medium.

Two common types:– Floppy disks– Hard disks

Floppy DisksFloppy Disks and Drives and Drives

Floppy disk characteristics

– Typically 3½ inches in diameter.

– Typically hold 1.44 megabytes.

– Inserted into floppy disk drive to be read from or written to.

Floppy Disks and Drives, Floppy Disks and Drives, Cont’d.Cont’d. Disk is divided into tracks, sectors, and clusters.

The disk’s file directory keeps track of the contents of the disk so files can be retrieved (by filename) at a later time.

Floppy Disks and Drives, Floppy Disks and Drives, Cont’d.Cont’d.

Using floppy disks– Must be inserted into the proper drive in the proper

direction. – Should not be removed when the disk is being

accessed.

High-capacity removable magnetic disks and drives– Zip disks (750 MB)– SuperDisks (240 MB)

Hard Disk DrivesHard Disk Drives

Hard drive characteristics

– Metal disk onto which data is stored magnetically.

– Disks are usually permanently sealed inside the hard drive—allows faster speeds and storage of more data than removable systems.

– Can be internal or external.

Hard Disk Drives, Hard Disk Drives, Cont’d.Cont’d.

Hard drive characteristics, cont’d

– Organized into tracks, sections, clusters, and cylinders (the collection of tracks located in the same location on a set of hard disk surfaces).

– Read/write head doesn’t touch the surface of the disk.

– Bumping PC when disk is being accessed or dust or other obstacles on a hard-disk system can cause a head crash and damage the surface of the disk.

Hard Disk Drives, Hard Disk Drives, Cont’d.Cont’d. Disk access time.

– Factors: seek time, rotational delay, data movement time

Can use multiple partitions.

Disk cache—strategy for speeding up system performance.

Hard drive standards (EIDE, SCSI, Fibre Channel, USB) .


Portable hard drive systems

– Offer large storage capacities and portability.

– Either entire drive or just hard disk cartridge is transported.


Storage systems for large computer systems and networks

– Storage servers containing racks of hard drives.

– Network attached storage (NAS).

– Storage area networks (SANs).

– RAID (for increased performance and/or fault tolerance).

Optical Disc SystemsOptical Disc Systems

Laser beams write and read data packed at very tight storage densities, many times finer than that of a typical magnetic disk.

Are typically 4½-inch discs, but can be a variety of shapes and sizes.

Data is stored optically on a continuous spiral track.

Can be CDs or DVDs.

Read-Only Discs: CD-ROM and Read-Only Discs: CD-ROM and DVD-ROM DiscsDVD-ROM Discs

CD-ROM discs cannot be written to or erased and typically hold 650 MB (e.g. music CDs).

DVD-ROM discs are similar to CD-ROM discs, but have higher capacity of 4.7 GB to 17 GB (e.g. movie DVDs).

Data is stored by burning pits into the disc surface that can be read using a laser beam.

Recordable Discs: CD-R, DVD-R, Recordable Discs: CD-R, DVD-R, and DVD+R Discsand DVD+R Discs

Recordable discs can be written to, but not erased or rewritten.

Burning a CD or DVD permanently records data onto the disc.

CD-R discs are commonly used to store data and for custom music CDs.

DVD-R/DVD+R discs are commonly used for home movies and other high-capacity applications.

Rewritable Discs: CD-RW, DVD-Rewritable Discs: CD-RW, DVD-RW, DVD+RW, DVD-RAM, and RW, DVD+RW, DVD-RAM, and Blue Laser DiscsBlue Laser Discs

Rewritable discs can be used in the same way as magnetic disks—data can be stored and erased as needed.

Phase-change technology is used to record data onto the

disc using reflectivity.

Rewritable discs can be erased by reverting the reflectivity back to the original state.

Blue laser discs are an emerging higher-capacity (23.3 GB) form of optical disc.

Other Types of Storage SystemsOther Types of Storage Systems

Magneto-optical discs

– A combination of magnetic and optical technology.

– Can store up to 9.1 GB per disk.

Other Types of Storage Systems, Other Types of Storage Systems, Cont’dCont’d

Flash memory media

– Chip-based storage.

– Solid state storage system—has no moving parts, so are more shock-proof and portable than conventional storage systems.

– Commonly used with digital cameras, digital music players, handheld PCs, notebook computers, smart phones, etc.

Other Types of Storage Systems, Other Types of Storage Systems, Cont’dCont’d

Flash memory media, cont’d.

– Common forms of flash memory:

• Flash memory sticks.

• Flash memory cards—CompactFlash, Secure Digital (SD), MiniSD, MultiMedia (MMC), SmartMedia, and xD Picture cards.

• Flash memory drives, such as USB flash drives.

Other Types of Storages Systems, Other Types of Storages Systems, Cont’dCont’d Magnetic tape systems—plastic tape that is magnetized to

represent data.

– Used primarily for backup and archival purposes (sequential access only).

– Read from and written to via a tape drive.

– Most tape media are in the form of cartridge tapes,

though detachable-reel tapes exist as well.

Other Types of Storage SystemsOther Types of Storage Systems, , Cont’dCont’d Remote storage—storage devices that are not directly

connected to your PC.

– Network storage—accessible through a local network.

– Online storage—accessible via the Internet and used for backup, as well as to transfer files to others.

Other Types of Storage Systems, Other Types of Storage Systems, Cont’dCont’d Smart card: credit-card-sized piece of plastic that contains

some type of computer circuitry.

– Holds less than a few megabytes.

– Commonly used to store prepaid amounts of digital cash or personal information.

– Smart card readers are attached to a PC or built into a cell phone, keyboard, or other device.

Other Types of Storage Systems, Other Types of Storage Systems, Cont’dCont’dHolographic storage

– Uses multiple laser beams to store data in three dimensions.

– Stores data in page format.

– No moving parts and simultaneous access to all data on a page.

Comparing Storage AlternativesComparing Storage Alternatives

Factors to consider: speed, expense, portability, storage capacity, and compatibility.

Most PC users require: – Hard drive– CD or DVD drive– Floppy drive– Additional devices (flash memory card reader, etc.) as

needed for the devices being used in conjunction with the PC (e.g. digital camera)

Operating SystemOperating System

Albert Kalim

System Software vs. System Software vs. Application SoftwareApplication Software

System software acts as a mediator between application programs and the hardware resources of the computer system.

Application software provides the tools to perform particular tasks on a PC, such as writing a letter, processing orders, playing games, composing ane-mail, and so forth.

The Operating SystemThe Operating System

A computer’s operating system is the collection of programs that manage and coordinate the activities of the computer system.

Primary responsibilities are management and control.

The operating system is the go-between, meshing the user’s application program with the resources of the system.

Functions of an Operating Functions of an Operating SystemSystem

– Booting the computer and configuring devices.

– Interfacing with users.

– Managing and monitoring resources and jobs.

– File management.

– Security.

Processing Techniques for Processing Techniques for Increased EfficiencyIncreased Efficiency

Multitasking—the ability of an operating system to work with more than one program (task) at a time.

Multithreading—the ability to process multiple threads within a program at one time.

Time-sharing—technique for multiple programs to share processing on a rotating basis.

Processing Techniques for Processing Techniques for Increased EfficiencyIncreased Efficiency, , Cont’d.Cont’d.

Multiprocessing—the ability to use multiple CPUs to process multiple jobs.

Parallel processing—the ability to use multiple CPUs to process a single job faster.

Coprocessing—utilizing special processors for specialized chores (e.g. math coprocessor).

Processing Techniques for Processing Techniques for Increased EfficiencyIncreased Efficiency, , Cont’d.Cont’d. Memory management, such as the use of virtual memory.

Buffering and spooling– A buffer is an area in RAM or on the hard drive to hold

input and output on their way in or out of system.– The process of placing items in buffer so they can be

retrieved by appropriate device is spooling.

Differences Among Operating Differences Among Operating SystemsSystems

Command line vs. graphical user interface.

Personal vs. network operating systems.

Types and numbers of processors supported.

Operating Systems for Operating Systems for Desktop PCs and ServersDesktop PCs and Servers PC operating systems are usually designed for use on

either:– Desktop PCs (personal operating systems)– Network servers (network operating systems)

Some operating systems have versions for both; some personal operating systems have limited networking capabilities.

DOSDOS

PC-DOS and MS-DOS were the dominant operating systems until the early 1990s.

DOS traditionally used a command-line interface; it is not widely used today.

WindowsWindows

Many versions of the Windows operating system have existed over the last several years.

– Windows 3.x (an operating environment over DOS, not an operating system).

– Windows 95 and Windows 98 (personal operating systems).

– Windows Me (personal operating systems for home PCs).

– Windows NT (network operating system).

WindowsWindows, , Cont’d.Cont’d.

– Windows 2000 (network and professional operating system).

– Windows XP (latest version that replaces both Windows 2000 and Windows Me for home and office PCs; based on Windows NT).

– Windows Server 2003 (latest network version).

Mac OSMac OS

Mac OS is the proprietary operating system used with Apple computers.

Mac OS has a graphical user interface.

The newest version is Mac OS X Version 10.3.

UNIXUNIX

UNIX is a commonly-used, high-end PC and server operating system.

Not built around any one particular family of microprocessors—can be used on a variety of computers.

Though traditionally a command line operating system, newer versions of UNIX use a GUI.

LinuxLinux

Linux is a version of Unix originally created in 1991.

Linux is open-source software; has been collaboratively modified by volunteer programmers all over the world.

Traditionally a command line operating system; many versions now use a GUI.

Recent increased support from big name companies (Sun, IBM, HP, and Novell, for instance) has increased the use and support of Linux.

NetWareNetWare

One of the most widely used operating system on PC-based networks.

NetWare provides a shell around the users’ local desktop operating systems so they can interact with network resources.

OS/2 and OS/2 WarpOS/2 and OS/2 Warp

OS/2 is an operating system designed by IBM for high-end PCs.

Available in both server and client versions (for accessing an OS/2 server).

The newest versions is called OS/2 Warp 4.0.

SolarisSolaris

Designed for Sun computers.

Can run on desktop PCs, servers, and some supercomputers.

The latest version is Solaris 9.

Operating Systems for Operating Systems for Handheld PCs and Mobile Handheld PCs and Mobile DevicesDevices

Windows Embedded—designed for non-personal computer-based devices (e.g. cash registers).

Windows Mobile—designed for handheld PCs, smart phones, and other mobile devices.

Palm OS—designed for Palm handheld PCs.

Symbian OS—designed for use with smart phones.

Operating Systems for Larger Operating Systems for Larger ComputersComputers

Larger computers typically used operating systems designed specifically for that type of system.

Many mainframes and supercomputers today are running Linux.

A group of Linux PCs linked together to computer at supercomputing levels is called a Linux supercluster.

Utility ProgramsUtility Programs

Utility program—a type of systems program written to perform a specific system task, usually related to managing or maintaining the system.

Many utilities are built into operating systems as well as being available as stand-alone programs.

File management programs—allow you to look at and manage the files stored on your PC (copy, move, organize into folders, etc.).

Utility Programs, Utility Programs, Cont’d.Cont’d.

Antivirus programs—find and eliminated computer viruses on your PC.

– Should be set up to run continuously and scan incoming files and e-mail messages.

– Should be set up to do a complete scan of your PC about once per week.

– Need to be updated on a regular basis.


Diagnostic programs—evaluate the computer system and make recommendations for fixing any errors found.

Disk management programs—diagnose and repair problems related to the hard drive.– Disk defragmentation programs rearrange the files on a

hard drive to store them in contiguous locations to speed up performance.


Uninstall utilities remove programs from your hard drive without leaving bits and pieces behind. – Programs should never be deleted from the hard drive

without using an uninstall procedure, unless there is no other alternative.

File compression programs make files smaller for archiving or sending over the Internet. – Compression programs can both compress (zip) and

decompress (unzip) files. – Common programs are WinZip for Windows users and

Stuffit for Mac users.


Backup utilities are programs designed to back up the contents of a hard disk. – You can usually specify certain files or folders to be

backed up or back up an entire drive.

– Businesses should back up frequently and regularly; individuals should back up their PC occasionally and all important files each time they are modified.

Recovery utilities are designed to help you recover from a major computer problem, such as rolling back your hard drive to an earlier state if it quits working after you install a new piece of hardware or software.


Encryption programs are used to secure e-mail messages and files that are sent over the Internet or other networks; can also be used with individual files stored on a hard drive.

Network and Internet utilities include:– Performance monitors– Logging programs– Directory services or identity management programs– Firewall programs– Antispam and e-mail filtering programs

The Future of Operating The Future of Operating SystemsSystems Will likely continue to become more user-friendly.

May eventually be driven primarily by a voice interface.

Will likely be used to access an increasing number of Internet resources and applications, such as Web based software and services.

Will likely continue to support more synchronization between an individual’s various computing devices, such as a desktop PC, handheld PC, and smart phone.

Software PackagingSoftware Packaging

Albert Kalim

SoftwareSoftware

The programs or instructions used to tell the computer hardware what to do.

System software allows a computer to operate and run application software.

Application software performs specific tasks or applications. Software products may be developed for a particular

customer or may be developed for a general market Software products may be

– Generic - developed to be sold to a range of different customers

– Custom - developed for a single customer according to their specification

Software Project DevelopmentSoftware Project Development

Writing Specifications: carefully stating what problem to be solved.

Developing Algorithms: formulate a technique to solve the problem:

- design phase: process of developing an algorithm.- Design: an algorithm with all supporting materials. Coding: translating the algorithm into a code computer can

understand. Testing: running the code with different sets of data and

find errors to be fixed (debugging). Maintenance: updating the software with current needs or

improving the program.

What are the attributes of good software?What are the attributes of good software?

The software should deliver the required functionality and performance to the user and should be maintainable, dependable and usable

Maintainability– Software must evolve to meet changing needs

Dependability– Software must be trustworthy

Efficiency– Software should not make wasteful use of system resources

Usability– Software must be usable by the users for which it was

designed

What is a programmer?What is a programmer?

Dictionary.com: “a person who designs and writes and tests computer programs.“ [maintain?]

Working conditions: Programmers generally work in offices in comfortable surroundings.

Many programmers may work long hours or weekends to meet deadlines or fix critical problems that occur during off hours. Given the technology available, telecommuting is becoming common for computer programmers.

What is a programmer? What is a programmer? Cont’d.Cont’d.

Employment: Programmers are employed in almost every industry, but the largest concentrations are in computer systems design and related services and in software publishers, which includes firms that write and sell software.

Large numbers of programmers also can be found in management of companies and enterprises, telecommunications companies, manufacturers of computer and electronic equipment, financial institutions, insurance carriers, educational institutions, and government agencies.


Training and Qualifications: - Employers are primarily interested in

programming knowledge, and computer programmers can become certified in a programming language such as C++ or Java.

- Because programmers are expected to work in teams and interact directly with users, employers want programmers who are able to communicate with non-technical personnel.


Job Outlook: Employment of programmers is expected to grow about as fast as the average for all occupations through 2012.

Jobs for both systems and applications programmers should be most plentiful in data processing service firms, software houses, and computer consulting businesses.


Earnings: Median annual earnings of computer programmers were $60,290 in 2002. The middle 50 percent earned between $45,960 and $78,140 a year. The lowest 10 percent earned less than $35,080; the highest 10 percent earned more than $96,860.

According to the National Association of Colleges and Employers, starting salary offers for graduates with a bachelor’s degree in computer programming averaged $45,558 a year in 2003.

Chapter 3, 4 and 5

Documents

Transcript of Chapter 3, 4 and 5