Finding Your Way Around a Computer
There are a number of terms that are basic to an understanding of computer operations.
Software, also called computer programs, refers to the commands that instruct the computer to perform tasks in a specific logical sequence. People who write these instructions are called computer programmers.
In contrast to software, computer hardware is the physical machinery that makes up the computer system. Hardware is the equipment that you see when you visit a computer room or computer retail store. Computer hardware is sophisticated electronic equipment that must be handled and used appropriately and safely, and maintained properly in order for the computer system to operate with optimal efficiency.
The heart of the computer system is the central processing unit (CPU). The CPU controls all the computer’s functions because it is made up of circuitry that interprets and car- ries out instructions written into software. The CPU also retrieves software instructions before decoding and executing them. The CPU chip, which acts as the electronic brain in a computer, is built using a state-of-the-art manufacturing process in which the average circuit feature has been shrunk to about sixty-five nanometers—small enough so that 100 transistors will fit into a single human blood cell (Goodin, 2006). There are about 291 million transistors in each processor. The components of the CPU are the arithmetic/logic unit (ALU), the memory, and the control unit (see Figure 1.7).
The ALU is that part of the CPU capable of performing mathematical calculations required for many data-processing applications. The memory of the CPU is made up of integrated circuitry in which information can be stored. The control unit of the CPU controls the flow of the computer’s operations, including data transfer, acceptance of input, functioning of the ALU, and other related functions (see Figure 1.8).
Through microphones and keyboards, instructions and data are entered into the com- puter system. Advances in speech technology have made possible the hands-free control of systems, applications software, and web searching. The personal computer keyboard is made up of keys that represent letters of the alphabet and numbers, as
well as special symbols such as @, $, %, and *, and special-function keys that instruct the computer to perform specific tasks. Wireless technologies now provide untethered keyboard communication with other computers, printers, notebooks, and peripherals.
A greater amount of memory capacity can be included in the CPU than was previ- ously possible. Adding memory to a personal computer is a simple and affordable process that most users can perform themselves. To determine the memory size of a personal computer system, it is necessary to understand several quantitative terms that apply to computer capability. A digital computer operates using a binary sys- tem of 0s and 1s. A binary digit is called a bit and is the smallest unit of digital information. A byte is the number of bits necessary to store one character of text.
- One byte = 8 or 16 bits
- One kilobyte (KB) = 1,014 bytes
- One megabyte (MB) = 1 million bytes
- One gigabyte (GB) = 1,014 MB
- One terabyte (TB) = 1,024 GB, or 1 trillion bytes
What is a terabyte or how much data will a terabyte hold? Fry (2006) answered as follows:
Using a handy unit of storage measurement: the Average Pop Song, or APS. Assuming an APS is four minutes and encoded at an ear-friendly 192 kbps, it will take up 5.6 megabytes (MB) of space. That means a 1 terabyte (TB) drive should hold nearly 179,000 APS, or nearly 14,000 albums.
Not only is capacity increasing, but speed also is part of the picture. As the Fry quote suggests, thousands of bytes are moved per second (kbps).
A major advantage of personal computer systems is that extra memory space can be added simply and quickly as the needs of the user expand. Extra memory space allows the system to operate with greater speed and efficiency. More complex pro- grams with lengthier instructions can be stored and run on a system to which extra memory space has been added.
There are two major types of semiconductor memory: random-access memory (RAM) and read-only memory (ROM). RAM is designed to store new data and pro- grams. Data and program instructions are entered into the memory of the central processing unit and then accessed, or retrieved from memory, in random fashion. RAM is not permanent memory. For example, if the computer system loses power during operation, the information stored in RAM is lost forever. To maintain pro- gram instructions and data in the assigned RAM locations, the system must refresh its memory. The system does this by supplying small amounts of electricity to memory locations at the rapid speed of several hundreds or even thousands of times per second. In contrast to RAM, ROM (read-only memory) is comprised of computer chips that have had program instructions manufactured into them per- manently. Information stored on ROM chips cannot be lost in the event of a power failure.
Memory Storage Devices
Another essential part of computer hardware is the memory storage device. Stor- age devices retain data and instructions outside of the computer’s central pro- cessing unit so that information is not lost when the computer is turned off. The common storage device in use for computers in general is the magnetic disk drive.
Each disk has two recording surfaces: top and bottom. On the recording surfaces are concentric circles mov- ing outward from the center of the disk to its edge. In- side the disk drive are mounted several read/write heads that record and retrieve information on magnetic disks.
Information stored on magnetic disks is relatively safe from loss. Loss of stored material may result from writing too much information onto a disk. Disks may also be erased by a computer-controlled device called a bulk eraser. Accidental loss of information stored on magnetic disks is unusual, though; this fact adds to the popularity of magnetic disk storage.
The floppy disk, which is rapidly becoming obsolete, functions similarly to the hard disk. Floppy disks (or diskettes) have a diameter of 3.5 inches and are enclosed within a hard plastic container. Floppy disks can now hold over one hundred times the information once stored on a 5.15-inch disk. Many other types of memory devices exist with even greater storage capacities. They include CD-ROM (compact disc read-only memory), CD-RW (compact disc rewritable), DVD (digital versa- tile disc), various types of data cards, and the use of net- work capabilities. Pocket and mobile drives can be used to store data externally (see Figures 1.9 and 1.10).
USB memory drive devices, often referred to as memory sticks, are convenient and popular. Toshiba recently announced microSD memory cards, and Hewlett Packard is supporting the Memory Spot (sometimes referred to as a smart object), which is smaller than a grain of rice. These devices not only can hold more data but their transmission of data is significantly faster. The memory capabilities of these new devices change with each new version. Fry (2006) reports that terabyte (TB) or trillion byte memory devices are now available.
Scanners are another method of entering information into the computer. Text scanners can read textual information printed on a page from any source. Image scanners read black- and-white and color images. These scanners convert the analog information to digital
information. Some scanners also convert text to speech.
Still other methods of inputting information are optical character readers (OCRs), optical mark readers (OMRs), and bar-code readers. For example, OCRs read the characters on the bottom of personal checks, and are also used to sort mail at a post office. Some uses of OMRs are to score objective tests for which the answers have been blacked in, to control the inventory of library books, and to monitor classroom attendance.
Display devices enable humans to see what in- structions are being given to the computer; to respond to erroneous information; to enter data and verify data for correctness; and to see the output, or final product, of the computer’s op- eration. Personal computer systems rely on a variety of video screens for display purposes. Many computers can be adapted for use with ordinary television screens, the most common video screen in our society. Video games that plug into the family television set are popular examples (see Figure 1.11).
With improvements in flat panel technology and lower-cost versions, liquid-crystal displays (LCDs) will continue to replace cathode-ray tube screens (CRTs). LCDs are often used to project for presentations and classroom lessons (see Figure 1.12). The next genera- tion of displays for television and computers is HDTV (high-definition television). This display provides much clearer images and displays. The advent of HDTV will mean the demise of one of the last vacuum tubes—the television picture tube. Ultra thin video screens are coming in all shapes and sizes, including video tiles for walls, windows, car visors, and any flat surface. The future for displays is unlimited.
Once the computer has completed its data-processing function, it is often necessary to generate some human-readable, permanent copy of the resulting output. A record of computer transactions printed onto paper is referred to as hard copy and it is often necessary for filing purposes or for reporting the results of data processing to others.
Dot-matrix printers, which printed text by actually impacting the paper with a printing element, have largely been replaced by two newer printer types, the inkjet and laser. Inkjet printers electrostatically spray small ink droplets from a nozzle onto the paper. Laser printing employs some design concepts that have been used in pho- tocopying machines. Laser printing is much quieter than impact printing and is ca- pable of printing copy of nearly typeset quality. The initial cost of a laser printer is more than that of a matrix or inkjet printer. However, the durability of the laser copy and the avoidance of smudging and fading problems give laser printers the advan- tage over inkjet printers.
An emerging color printing technology is high fidelity or Hi-Fi. Although it is still expensive, Hi-Fi color technology provides an alternative to traditional four-color offset printing methods. By increasing the number of standard colors from four (cyan, magenta, yellow, and black) to six, seven, or even eight colors, the accu- racy of reproducing screen images increases.
TABLE 1.1 Decreasing Cost of Computer Operations
|Generations||Technology||Cost per 100,000 Computations|
|Fourth||LSI||Less than 0.01|
Personal computers with their multimedia capabilities are continually being integrated into the classroom curriculum. Using personal computers and the World Wide Web, educators are creating new learning environments. Within these environments, teachers become facilitators and students become constructors of knowledge. Together, teachers and students become knowledge navigators, a term coined by John Sculley, past CEO of Apple Computers.