If you already understand Windows and concepts about hardware, you may move to the next section.
Identify hardware related aspects of computing including:
describe the basic computer architecture.
define computer terms
identify input, output, storage and interactive
EVALUATION STRATEGY: Objective examination (Content on this topic will be included in Quiz 1).
Assigned Reading Activity (Most of this information will be on quiz 1).
Regardless of the type of computer, mainframe or micro, first generation or fifth, each one has the same kind of basic functions: input, process, store, and output.
Input. Computers are able to accept information from primary input sources, such as the keyboard, mouse, and microphone, and from secondary storage systems, such as disk drives and tapes.
It should be noted that the different spellings, disk and disc, refer to two different kinds of technology. When the word is spelled disk, the storage mechanism is magnetic; when disc is used, the technology is optical, such as videodisc and compact disc.
Process. The computer can manipulate information (data) in a variety of ways, depending upon the nature of the software and the needs of the user. The computer has three main processing functions (arithmetic operations, logical comparison, and storage\retrieval). A computer can quickly solve problems in mathematics that would take several lifetimes to achieve with a pencil or a calculator.
The central processing unit (CPU) is commonly called the processor and refers to the heart of the computer itself, the control unit and the arithmetic/logic unit (ALU). Data are received, manipulated, stored, and displayed according to a rapid series of instructions based on the binary number system 1 and 0 (for "on" and "off") that represent the presence or absence of electrical impulses. Any character entered, such as a numeral, letter, or symbol must be represented in binary code. For example, the basic decimal and binary equivalents are: 1 = 0001, 2 = 0010, 3 = 0011, 4 = 0100, 5 = 0101, 6 = 0110 , 7 = 0111, 8 = 1000, 9 = 1001, and 10 = 1010.
Each 0 and 1 in binary code is known as a bit, which is the fundamental building block of machine code as well as the most basic measure of capacity. A particular series or permutation of bits in a string of eight is called a byte, and is used to represent one character, such as a letter or digit.
Capacity has been measured in terms of K which is actually 1024 bytes, but as a practical matter the "24" has been dropped so that K refers to 1000 bytes. Thus, a 640K computer describes its capacity as roughly 640,000 bytes or characters of information. Storage systems for microcomputers are now coming available with capacity measured in megabytes (millions) and gigabytes (billions) of bytes.
The CPU handles both primary and secondary memory functions of the computer, or the ROM (read only memory) and RAM (random access memory). ROM is built in by manufacturers and contains the fundamental operating instructions for the computer. Nothing can be "written to" ROM by the user because this would destroy the computers ability to function. Each time the computer is turned on, the ROM instructions are available. RAM, however, is volatile information that is temporarily stored in memory and unless stored on a disk or printed out, will be lost when the power is turned off. Macintosh computers use the term "desktop" to refer to RAM.
The basic speed of a computer is measured in megahertz (Mhz) or millions of pulses per second. Older computers worked at 4, 8, or 16 Mhz. The IBM or compatible computer with an 80286 microprocessor, commonly just called a "two eighty six," operates at 12MHz; the 80386 operates at 20MHz, and is faster than the 80286. An 80286 computer can add about 10,000 numbers in 32 seconds. New computers now operate at 450 to 500. By contrast, a supercomputer was originally defined as one that can perform 5 million floating-point arithmetic operations per second, 5 megaflops. Today supercomputers can perform one-billion floating point operations per second, or one gigaflop (GFLOP). Other measures of speed often used in describing computers are millions of instructions per second (MIPS), millisecond (thousandths), microsecond (millionths), nanosecond (billionths), and picosecond (trillionths).
Computers are also referred to as 8-bit, 16-bit, and 32-bit machines. This means that a machine can process 8, 16, or 32 bits at a time. Mainframes are 32 bit machines, but today many microcomputers are 32 bit machines.
Store. A computer can store information temporarily in random access memory (RAM) or permanently by using hard disks, floppy disks, and optical storage systems (e.g., CD-ROM). Incredible amounts of information can be stored electronically. The computer can retrieve data quickly, one of the greatest benefits of computer usage and a major reason why it has been adopted by businesses.
Output. The computer can "print" to a screen, print to paper, print to other disks, and print over cables, telephone, and satellite for transfer to other persons. Once the data are arranged for display, the appearance can be quickly changed by adjusting margins, fonts, and other layout characteristics. Output devices are machines that accept computer information for specific purposes, the printer, monitor, speaker, and modem.
Components of a Computer
In order to store, process, retrieve, and display information, a computer has related hardware components: Input Devices, Input/Output Devices, and Output Devices.
An input device permits entry of information into a computer and this information is interpreted as "machine readable" track ball, microphone, optical character reader, and touch screen/light pen. With advances being made in voice recognition and control, computers in the future may not require keyboards because the computer may react to direct control by the human voice.
The Keyboard. Regardless of the type, the keyboard has several common functions which relate to its heritage from the typewriter and its new use as an electronic device. Most keyboards installed on computer systems are sometimes referred to as "QWERTY" boards, derived from the first five letters on the upper row. This keyboard was apparently designed for the first typewriters in order to prevent keys from clumping and sticking together. As a standard layout, the letters and numbers on the keyboard have not changed, but many different types of keys have been added to the computer keyboard. One recent innovation is the development of modular keyboards, making it possible to install different parts of a keyboard on a base according to personal preferences.
Function Keys. Most keyboards have a row of function keys indicated by F1, F2, F3 . . . across the top row or along columns to the left. Older keyboards have F keys up through F10 and newer versions go through F12. This is important because some newer and revised software require F11 and F12 keys to operate. Function keys cause the computer to react to commands in software.
The Cursor. A cursor is a blip on the screen at the point where information may be entered by the keyboard. Placement of the cursor is made by using the Cursor Keys, which have arrows on them for up, down, left, and right. They also usually incorporate Page Up, Page Down, Home and End controls. The arrow keys move the cursor one space at a time in any direction selected, and with certain programs, a word, line, or paragraph.
Editing Keys. Two special keys remove or add text to a page, the delete (Del) key and the insert (Ins) key. Ordinarily, the Del key removes one character at a time when depressed, and the Ins key permits insertion of text.
Special Keys. All keyboards have special keys that were never found on the typewriter. There may be new keys developed in the future when new applications emerge. The most common special keys are the Escape (Esc), Alternate (Alt), Control (Crtl), and Print Screen (Prt Sc). Esc is used frequently to leave the control of certain software functions. Crtl is combined with the F keys and others to permit different commands.
The Mouse, Track Ball, Touch Screen, and Light Pen. The mouse, track ball, touch screen, and light pen are all forms of pointing devices that can input data and control the cursor or pointer on the screen. The track ball is replacing the mouse in some applications, but it is not yet as popular. The touch screen and light pen are used in "kiosk" programs such as those found in stores and malls to provide directions or even order merchandise. The more common mouse is often found working in tandem with a keyboard for special software applications.
Using a mouse requires the ability to "click" and "double click" and sometimes to "triple click."
Click means to quickly depress the button on a mouse to cause the pointer on the screen to execute programs. This is done by pointing at certain parts of the "pull down menu" or an icon and clicking the mouse, according to specific requirements of the program. Another function is "click and drag," which means to press the button down but not let it up so that a certain function may occur.
Microphone. Although not very common yet, the microphone is available for use as an input and control device with current software programs. In the future, as costs diminish, microphones may actually replace the keyboard and the mouse, or at least relegate them to more infrequent use. Advances in voice recognition, the ability of the computer to understand and react to human voice commands, are making steady progress.
Optical Character Reader (OCR). A variety of devices can copy text, graphics, and codes directly into a computer. Photographs, pictures from magazines, and text can be saved for use in many kinds of programs. As the prices of these products continue to drop, schools will find them useful for a full range of activities.
Input/Output Devices are disk drives and discs, magnetic tape, and disk packs that input and transfer information while a program is running. Input/Output devices are essential to the operation of the computer and are distinct from devices that are solely for input or output. For most microcomputer users, the essential input/output device is the disk drive.
Disk drives "read" the information stored on files in a hard disk or on the disks inserted into disk drives; these are the instructions to the computer or the data the computer will use in particular applications. There are two general classifications of disk drives for microcomputers: hard disk and floppy disk drives.
Floppy Disks. Floppy disks that were loaded into mainframes were originally 8 inches in size and could store 1.25M characters. The term "floppy" was used to describe the original 8-inch disk which was very flexible. Made of the same magnetic tape as audio cassettes, it was easy to bend inside a flimsy envelope, thus floppy. Today there are one size for most microcomputers: the 3 1/2 inch-disk, which is sometimes called the minifloppy and microfloppy, respectively.
The disk drive operates by spinning the disk around while the access arm, similar to a needle on a stereo system, either reads or writes on the disk by detecting or creating magnetized spots. The disk is comprised of concentric circles called tracks. Some disks are single-sided and others double-sided, meaning that encoding can be done on one or two sides. The single-density disk can store data at a rate of one bit every eight microseconds with a maximum capacity of 100K bytes. Double-density disks can record one bit in half the time, or every four microseconds, doubling the capacity. When a disk is formatted, it is divided by the disk drive into addressable sectors. Each sector is a wedge which can be identified by the location number given it during formatting. When data are placed on the disk, as in word processing or spreadsheet problems, they are stored in the various sectors.
Hard Disk. Because of the need for greater storage and the ability to back up programs, many microcomputers are also equipped with hard disk drives that are internal to the computer. Although there are many sizes of such drives, the most common are 20M and 40M. A computer with an internal hard disk drive and two external drives will have three drives designated usually as "C" for the hard disk, and "A" and "B" for the two external drives.
There are many kinds of devices that may be regarded as output, including the monitor, printer, modem (for modulate/demodulate), and any other kind of devices that can understand and carry digital information. For most users, the monitor and printer are of greatest importance.
Monitors. There is a wide range of options available in selection of monitors. In the recent past, when most monitors were essentially television sets, they were often called CRT's---for cathode ray tube---and some are referred to as video display terminals (VDTs). More sophisticated software programs, greater memory capacity of computers, and other factors have created a demand for specialized monitors with higher resolution. Monitors display graphics and text with dots or pixels (picture elements). The quality of a picture is determined by the number of pixels; the more pixels packed into the screen, the better the resolution (sharper the image). Color monitors today come in four popular types:
_ CGA (color graphics adapter): a color graphics standard of 640 X 200 pixel resolution, which is unacceptable for word processing because of eye strain.
_ EGA (enhanced graphics adapter): a color graphics standard that displays text with 640 X 350 resolution.
_ VGA (virtual graphics array): a color graphics standard of IBM that displays 16 colors or 256 colors (with a proper graphics card) and 640 X 480 pixel resolution.
_ SVGA (Super virtual graphics array): 256 colors and 1024 x 768 resolution.
Printers. Not too long ago the most common type of printer was the dot matrix, but today ink jets and lasers are predominant. Ink jet sprays ink onto the page through an aperture rather than impacting with a ribbon. The laser jet prints text and graphics of high quality on a page through a photocopy technique. The laser beam reflects off a rotating disk of the fonts, forming an image on the paper which is processed with toner, a substance of the appearance of very fine, black powder.
Modems. Another important output device for transferring data is the modem (modulate/demodulate) which can transfer data over a telephone line or fiber cable. In order to do this, the switched telephone network must be used so it is necessary that data be put in a form that can be handled by the line, or in the 300 to 3400 HZ used for voice transmission. In this case, the computers are able to understand one another regardless of the operating systems used because the communications are first translated into ASCII code (American Standard Code for Information Interchange), causing data to conform to a particular code universally recognized by modems and computers.
As in other aspects of computing, speed is a concern. In modems, speed is measured in bits per second (bps) and the ultimate speed is called the baud rate. Baud rates for modems range from 2,400 to 56,000, the most common. A modem can only receive information at its maximum rate. Modems are now becoming smaller and installed as part of the internal workings of some computers. Most laptop computers, for example, have a built in modem requiring that a telephone line be snapped into the port connection. As more avenues are open, such as television, DSL, and other options, the speed of modem transfer may increase dramatically for common use.
When a computer is turned on, which is also called "booting" the computer, the electrical current establishes connections in the circuitry through the computer's operating systems software, making it possible for all parts of the computer to interact and accept instructions. Unless a program is created on the computer, most users will install applications software for a particular purpose, such as word processing, data base, spreadsheet, a game, or computer-assisted instruction. The applications software will be stored (in secondary memory) on a floppy disk or on the hard disk. As long as the applications software is written in a code that can be read by the particular operating systems software, the program will execute and run smoothly.
Booting computers can be done by turning on and off the machine at the
power switch (called a cold boot) and by warm boots.
Many computers today require that computers be shut down with a specific procedure so that there will not be loss of data.
Formatting or Initializing Disks. In order for a new, blank disk to be used as a "data disk" or disk for word processing, spreadsheets, or some other purpose, it must be prepared to operate in the proper disk operating system. The process of formatting or initializing simply lays down instructions on the disk to make it function properly.
Applications Software. In the beginning the only way to use a computer was to learn how to program it. Programming has changed dramatically with each stage of computer development. In the beginning, programming was very tedious work because programs had to be created directly in machine readable code. The early years of programming were dominated by machine language followed by assembly language. Later, high-level languages appeared, meaning higher than the 0s and 1s of machine language. The two most prevalent were FORTRAN (derived from the name Formula Translator) and COBOL (derived from Common Business-Oriented Language). Languages such as BASIC, PASCAL, and C emerged with the popularity of microcomputers. With the development of high-level languages and the software market created by the sales of millions of personal computers, applications software packages have been developed. They are often also called "off-the-shelf" software for the obvious reason. Thus, most people can use a vast array of programs without having to program the computers. There are now new forms of programming, such as Java and Flash.
Files. In word processing, databases, or spreadsheet software,
it is necessary to format/initialize a disk so data can be saved to the
disk. For example, if you write a letter, it is first necessary to have
the blank disk prepared properly (formatted), and the next step is to save
files on the disk. The name given and the way to create a file will ordinarily
be explained by the particular applications software package that is used.
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