A computer is a machine that can handle large amounts of information at an incredible speed. Computers can only solve the problems they are programmed to solve.
A typical computer set-up might include a monitor, keyboard, mouse, printer, internal disk drive, hard disk drive, CD-ROM drive, modem, and speakers.
A computer performs four tasks.
receives input such as figures, facts, or sets of instructions.
stores information by placing it in its memory.
processes the data by acting on the information.
outputs the information by generating the results of the processing.
The computer chip, synonymous with integrated circuit, is a silicon wafer that holds from a couple of dozen to millions of electronic components.
Computer chips are encased in plastic to protect them.
Tiny circuits are etched on the chip through a process called Large Scale Integration (LSI) or Very Large Scale Integration (VLSI), which allows the silicon chips to be produced economically in large quantities. Today, there are millions of transistors on a single chip.
the microcomputer, the RAM, ROM, and CPU chips, along with other components, are plugged into a printed circuit board. The other side of the board is printed with electrical conductive pathways between the components, which can number in the hundreds of thousands or millions.
The central processor is the computing part of the computer. A personal computer's central processor, or CPU, is contained on one single chip called a microprocessor, smaller than a fingernail. This essential unit controls the way the computer operates and consists of these components:
The control unit verifies that the computer carries out instructions, transfers instructions to the main memory for storage, and relays information back and forth between the main memory and ALU (Arithmetic and Logic Unit).
The ALU carries out all the arithmetic operations and logical decisions.
The central processing unit needs memory as a way to store information while it is not being processed.
Two types of chips take care of the computer's internal memory: read-only memory chips (ROM) and random access memory chips (RAM). ROM chips store information permanently in the computer's memory, whereas RAM chips allow for temporary storage and modification or deletion of information. RAM is referred to as volatile memory because of its temporary nature. Whenever the computer is turned off, the user loses whatever information is in RAM.
The basic unit of storage for RAM is a byte, which measures the space available to hold letters, numbers, and characters. In the 1970s, RAM was measured in kilobytes (K) or thousands of bytes, but today RAM is measured in megabytes (MB). The number of RAM chips a computer has in its memory determines the amount of information that can be retained in memory, the size and number of programs that can be run simultaneously, and the number of data that will be processed immediately.
All computer input is converted into binary numbers consisting of two digits, 0 and 1, known as bits, short for binary digits. An instruction read as 1 tells the computer to turn on a circuit, and an instruction read as 0 tells the computer to turn off a circuit. The computer can represent letters, numbers, and symbols by combining individual bits into a binary code.
Operating Systems
The operating system of a computer handles the transfer of data and programs to and from the computer's disks. The operating system controls the computer's components and allows them to communicate with each other. The abbreviation DOS stands for disk operating system.
Different computers have different operating systems. The same computer may also have more than one operating system available to it. Some well-known operating systems are MS-DOS, Microsoft Windows, Microsoft UNIX, and Macintosh OS X. Because a single, standard operating system does not exist, not all computers are compatible. Many companies are seeking a solution to the compatibility problem.
The majority of computers currently have hard disk drives, and their operating systems are installed from CD-ROM onto the hard disks. Previously, when operating systems were stored on a disk, the procedure of starting the computer to load its operating system became known as "booting the system." Today, the procedure of starting the computer system is still referred to as "booting the system," even though the operating system is on a hard disk, and the user simply turns on the computer.
Macintosh, Windows, and Linux have different operating systems.
The new Macintosh operating system, Mac OS X Panther, has translucent buttons and an aqua interface. Mac OS X has folders, applications, documents, storage, minimized windows, QuickTime movies, digital images, links to websites, and applications needed for instant access. The system is built to access the Internet easily. Macintosh OS Panther combines Mac OS X with UNIX and the ease of use of the Macintosh.
The Windows XP operating system is a combination of the best features of Windows 2000, Windows 98, and Windows Millennium Edition, such as plug and play. The system is built to take advantage of the Internet and provide support for mobile users. The system eliminates menu clutter, is less artistic, and is more analytical-looking than the Macintosh.
Linux's source code is freely available to anyone and runs on a variety of hardware platforms. Linux is stable, cost-effective, and secure, can be used for networking and software development, and is increasingly popular.
Hardware, Software, and Input Devices
The hardware of a computer system includes the electronic components, boards, wires, and peripherals.
The software instructs the computer hardware to perform various tasks.
Input devices give information to the computer system, so that it can perform its tasks.
The most popular input devices used in the classroom today are the keyboard, mouse, trackball, touchpad, and joystick.
Alternate input devices include optical scanning devices that utilize laser capabilities.
Many schools and school districts use the optical mark reader (OMR) to grade standardized tests. The amount of reflected light on paper is reflected by a photocell, and when a mark is made on the paper, it blocks light from reflecting.
The scanner is affordable and useful for desktop publishing, faxing, and optical character recognition (OCR). The scanner scans a printed page and converts it into text, eliminating the need to retype a document. Scanners can also digitize photographs or line art. Handheld scanners fit in the palm of the hand, while flatbed scanners rest on desktops, and the overhead scanner is used for large documents. Scanners differ in resolution, or degree of sharpness; the more dots (pixels) a scanned image contains, the sharper it is.
Digital cameras record images in digital format and are especially suited for desktop publishing. Traditional cameras use film, while digital cameras use a charge-coupled device (CCD) that is readable by the computer. Digital cameras are still evolving and are regularly upgraded by manufacturers in their resolution, price, and size.
Videoconferencing cameras or Webcam cameras offeran easy way to capture still pictures and moving images. They are especially suited to creating presentations, Web pages, live video, and e-mail video and pictures.
Handheld computers such as electronic organizers are small mobile computers that accept input through a penlike instrument called the stylus that is used to write on the computer screen. They can be used to receive and send faxes, send e-mail, keep a calendar, and collect information from distant databases. The Alpha Smart 3000 is an example of a quality handheld computer for classroom use. A checklist of features to consider when purchasing a handheld computer can be found on p. 44.
Output devices show the results of what the computer has accomplished.
The printer gives a permanent record of the user's work by producing a printout, or hard copy.
The dot-matrix printer was widely used for years but has disappeared from classrooms, with advances in ink-jet technology. The dot matrix printer is an impact printer that operates with tiny metal rods or pins striking an inked ribbon.
The ink-jet printer uses a nozzle to spray a jet of ink onto paper. Ink-jet printers produce high-quality output, have few moving parts, and are quiet and inexpensive. They are slower than laser printers.
Laser printers produce near-professional quality print and operate like a copy machine, by tracing an image using a laser beam controlled by the computer. Laser printers produce text and graphics with high resolution.
Screen displays
The monitor is an essential piece of equipment. The two most frequently used types of monitors are the cathode ray tube (CRT) and the liquid crystal display (LCD). CRT traditionally refers to a vacuum tube that is used as a display screen in a video terminal or TV; currently, the term refers to the entire monitor rather than the tube. The best CRT monitor is the red, green, blue (RGB), because it generates a better image than the television.
The classroom teacher can use three methods to demonstrate a computer program or concept to the entire class: the LCD projection panel, projectors, and scan converters.
The LCD panel is a projector that receives computer output and displays it on a liquid crystal screen placed on top of the overhead projector.
The LCD projector connects directly to a PC, Mac, VCR, or video source and is an excellent way to view a software program or see an Internet site. These projectors range in price from $2,000 to $3,500.
The scan converter is a useful presentation device for teachers on a budget. This converter can turn any standard television into a large screen display and is both Mac and PC compatible.
Storage Devices
Storage devices provide for both storage and retrieval of information. The six most commonly available storage devices are the floppy disk, Zip disk, USB drive, hard drive, CD-ROM/CD-R/CD-RW disk, and DVD/DVD+R disks.
IBM introduced the floppy disk in 1971. The most popular size of floppy disks is 3.5", but it is not adequate for multimedia, and many laptop computers are being offered without a floppy disk drive today.
Iomega Corporation introduced the Zip drive in 1995. The Zip drive is a removable storage device, either internal or external, that provides for 750MB of storage.
The current rage is the USB drive, smaller in size and capable of storing more information than a Zip disk. The USB mini flash drives, usually the size of a fat pen, fulfill data-exchange needs for USB-equipped PCs. They can easily store multimedia and document files.
The hard drive provides increased storage capabilities and faster access and is incorporated into the computer system. The hard drive can wear out in 3 to 5 years, and the optical disc is its likely successor.
Optical discs, with a 30-year life expectancy, are direct access disks that come in the form of compact discs (CDs), compact disc read-only memory (CD-ROMs), CD-R and CD-RW (recordable and rewriteable), Digital Versatile Discs (DVD-ROM), and DVD+R (Recordable). Rewriteable disks can be erased and used repeatedly.
Input/Output Devices
Two important input/output devices include the fax machine and the modem.
The facsimile (fax) machine allows the user to transmit text and images between distant locations, and the modem lets two computers communicate with each other.
Hardware Selection Criteria
A computer's compatibility with other computers is a key consideration, along with its ease of use, documentation, weight and size, durability, and choice of operating system, either Macintosh or Windows.
A very important consideration is the computer's random access memory or RAM. Today, many applications need 16MB or more of memory. Every time software publishers upgrade programs, they increase memory requirements to run all the features.
Whether or not a computer is powerful enough for the user creates a question of expandability. Upgrading the processor chip, increasing memory, adding special equipment and extra peripherals, and expansion slots are all considerations.
The speed at which the microcomputer accesses the information is an important criterion in selecting hardware. Speed depends on clock speed and word size. Clock speed is the number of electronic pulses per second and is measured in megahertz (MHz). The more pulses the computer has per second, the faster it executes instructions.
The user should test the keyboard for how comfortable it is to use. Keyboards have many ergonomic designs. Extended keyboards have additional keys that can be programmed to perform different functions and numeric pads that speed up number entry.
Hard disk space has become larger and less expensive, with some computers being sold with a minimum of 40 GB (gigabytes); the bigger the hard disk, the better.
The computer monitor is another important consideration.
The CRT is the most economical for word processing, spreadsheets, and educational software. The higher the resolution of the screen, the clearer the screen display. Resolution is expressed as the number of pixels, or linear dots, displayed on the screen.
Monitor size varies from 5" to 40". The size of the monitor should not be smaller than 15". The dot pitch and refresh rate should also be considered when purchasing a monitor.
Video RAM (VRAM), or graphic memory, is "a type of memory in a video display board that holds the image that appears on the video screen" (Freedman, 2003). Users should have at least 32MB of graphic memory, with 64MB or 128MB preferred.
Sound quality is important for playing musical compositions or educational games. A minimum of 32 voices is desired for realistic sound quality. A high-quality sound card can have up to 64 MIDI (Musical Instrument Digital Interface) voices.
Peripherals should be considered in terms of their quality, cost, cost to repair, and access time.
Hardware reliability and dealer support should be considered in terms of reputation and service.
Ease of operation and quality documentation for the computer must be considered.
Cost should be evaluated after comparison-shopping in stores and looking at advertisements. Repair costs, free software, warranties, and on-site repair should be part of the criteria for selection.
A hardware checklist can be used to rate different aspects of the user's hardware needs. See p. 50.
A Hardware Reference Guide on pp. 51-58 provides detailed descriptions and pictures of key hardware components discussed in the chapter.
