ANGOL SZÓBELI
High-level languages resemble English to some extent and a single instruction written in them, when translated into machine code, results in several instructions. The system program used to translate a complete high-level language program into machine code is known as a compiler, which is unique for each computer. Therefore, a computer needs its own compiler for the various high-level languages.
An interpreter, which is used mainly with microcomputers, can translate a high-level program into machine code line by line. There are several types of high-level languages. The user can choose from among them according to his needs.
In the largest computer installations laser printers are used, which are very fast and have a print rate of about 20,000 lines per minute. They print a whole page at a time by using a laser beam to bake the pattern onto the paper.
Output techniques keep being improved. One of the most promising methods (of the future) is voice output, which is based on speech synthesis. If the basic sound patterns making up speech are stored the computer can be programmed to put these basic sounds together in different combinations to produce speech. If the quality of "computerspeak" is improved, this technique may be used for language teaching and translation in the future.
Most new monitors are SVGA (Super Video Graphics Adapter) with a pixel configuration of 800 by 600 at low-resolution mode and 1,024 by 768 at high-resolution mode. The XGA (eXtended Graphics Array) also has a pixel configuration of 1,024 by 768. The higher resolution with more pixels provides a clearer, more detailed image. Monitors are also categori 23323r1719x zed by whether they display in black and white (monochrome) or color.
In order to connect a monitor to a microcomputer, you must have a graphics adapter board. Each type of monitor requires a different type of board. The graphics board plugs into an expansion slot inside the computer, and the monitor plugs into the board.
The matrix printer uses pins to print a pattern of dots in the shape of the required character. It is much faster than the daisy wheel printer as it has a print rate of about 200 characters per second. However the quality of print is not as good and is known, therefore, as Near Letter Quality.
The line printer prints one line of text at a time with the character set being on a moving chain or rotating drum where each segment has the full set of characters in raised form around its edge. This type of printer can have print rates of about 3000 lines per minute.
Non-impact printers use a special chemically treated paper and expose the characters onto it by heat, electrostatics or lasers.
The computer recognizes the need for adjustments, makes them, and then checks to see whether more adjustments are needed.
A master file contains all the current data relevant to an application. For example, a customer master file contains a record for each customer of a business. The record contains such fields as name, address, current balance, and recent payments. The master file is updated when new charges and payments are recorded. This update process can be accomplished with a transaction file or by capturing data at the time the transaction occurs. (This updating is known as point-of-sale processing.)
Reports can be very long. A report file holds a copy of a report in computer-accessible form until it is convenient to print it.
Word processing programs enable you to write, edit, format, save, and print a document with ease. Using word processing software, you can produce a high-quality document in much less time than if you used a typewriter. The reason is that word processing software separates document creation from document printing. With a typewriter, as soon as you type a word, that word appears on paper. If you need to correct a word in a typewritten document, you must erase the word somehow and then type the correction in the exact same spot. A word processing program, however, enables you to create a document, check it for spelling, edit it for style, format it for presentation, and save it for later retrieval.
Impact printers can produce carbon copies and are fairly loud, although covers are available to muffle the noise. In contrast, nonimpact printers are quiet. However, because nothing presses on the page, a nonimpact printer cannot produce carbon copies.
Impact printers can produce a page, a line, or a character at a time. Large computers use line printers. The main drawback to line printers is that they can produce only text-no graphics.
Many small computers use character printers. Although only one character can be produced at a time, many types of character printers can produce graphics as well as text. The most common character printers create images using a dot pattern.
Optical scanners can scan typed documents, pictures, graphics, or even handwriting into a computer. Photographs scanned into a microcomputer appear clearly on the screen and can be displayed whenever desired. The copy that the computer has stored will never yellow with age. Scanners convert the image they see into numeric digits before storing it in the computer. This conversion process is known as digitizing. Depending on the volume and type of material to be scanned, you can use flatbed scanners, sheet-fed scanners, and even small hand-held scanners. The small, hand-held scanners (priced at about $150) are most frequently used with microcomputers.
Video digitizers can capture input from virtually any type of video device - VCRs, televisions, camcorders. Audio digitizers can digitize music or voice from a microphone. It is fairly easy to capture a portion of a television show, add some music that complements the picture, and play back the result on a microcomputer.
New and exciting input devices are being developed continually. Sensing devices are used to monitor physical qualities like temperature, medical patients's vital signs, the systems in a car, or robotic systems.
Output devices are as varied and as innovative as input devices. From traditional printed output to audio output and robots, there are a multitude of forms of computer output.
More than 85 percent of the personal computers in existence are equipped with word processing programs. With word processing software, you can write, edit, store, and print your work. Very few people who have tried word processing would consider going back to a paper-and-pencilmethod!
Learning how to use a word processing program is an excellent step toward computer literacy. While you learn basic computer concepts, you learn a valuable skill also. This unit introduces the basic features of word processing.
Historically, word processing can be seen as the latest step in a long process. This process has placed the capability to print ones's work in the hands of the individual user.
Voice input and control systems have the potential of revolutionizing the way we communicate with computers. But there are many problems. The day is still to come when we can talk to our computers the way they do on Star Trek.
Computer scientists and linguists have been working on voice recognition systems for two decades. The major difficulty has been that people speak with different accents and intonations. For this reason, most successful voice recognition systems require a period of "training" while the system becomes accustomed to an individual's accent and intonation.
Most output can be divided into two categories: soft copy and hard copy. Soft copy is ideal when you are writing a document, playing a game, or reading the latest news. Soft copy is temporary; after you have finished with it, there is nothing solid to hold. You can however, transfer soft copy to a disk to transport it. Hard copy can be touched and carried. It is especially helpful if you need to have a colleague look at your work or you need to give your work to a supervisor or teacher.
When you think about viewing computer output, you probably visualize a monitor. Monitor output is soft copy; when you are done viewing it, you cannot pick up the output and move it. Monitor displays are the most common form of soft copy.
This software offers several advantages over a special-purpose word processor. One advantage is that the general-purpose computer can perform other tasks besides word processing. A second advantage is that word processing software can be frequently updated with new features and capabilities. Documents produced can also be imported into other programs. As you learn in this unit, desktop publishing programs can import documents from many word processing programs. Using a personal computer and word processing software to produce documents can dramatically improve your productivity.
Today word processing programs are the most popular category of software packages.
After the program has been keyed in, it must be tested. If it runs well and can perform the operations necessary to solve the problem the program can be stored on a storage device. If errors occur it is advisable to get a printout of the program, which makes it easier to find the bug.
Flowcharting is a basic step in programming because it shows the logical path the computer will follow in performing a program. Certain symbols are used to indicate the different steps which have to be carried out.
Let's take a flowchart as an example. It shows how to calculate tax on salary if there are only two tax rates: 30% for those who earn less than 20,000 pounds a year, and 40% for those who earn more than 20,000 pounds.
Microfilm stores images of reports on a roll of film; microfiche uses four-by-six-inch sheets of film to store images. Besides saving storage space, COM is less expensive than regular printed output. Producing output on microfilm or microfiche is also faster than printed output. COM devices can output in excess of 30,000 lines per minute. The major disadvantage of COM is that because of the small size, special readers are required in order to be able to read the film or fiche.
Probably the most intriguing output device is the robot. Most robotic devices consist of a single arm that can perform a preprogrammed task. Robotic devices are frequently used in manufacturing for such tasks as spray painting or assembling parts.
New sound cards even include the capability to have the computer read a text file to you while you continue working on a different application.
The second most common form of computer output is printed documents. Although a computer can operate perfectly without a printer, it is certainly helpful to the user to have one. Printed output is a form of hard copy.
Printers can be categorized by whether anything mechanical actually touches the paper; whether they do or do not produce a solid character; and whether they produce a page, a line, or a character at a time.
When a part of the printer presses the paper to form the character, the printer is considered an impact printer.
You may be surprised to learn that people are part of the computing process. Some computers, such as the computer chip that controls an automobile engine, function without human intervention. But even these computers were designed by people and occasionally require maintenance by people. Most computers require people, who are called users (or sometimes end users).
Some users progress beyond the basics of computer literacy. They learn the advanced features of application programs. With this knowledge, these users can customize an application program for a specific tasks. These knowledgeable people are called power users.
The invention of the printing press and the use of movable type revolutionized our means of communication. Johannes Gutenberg is credited with inventing the printing press in Germany in the 1450s, but movable type was used in Korea a half century earlier.
Before the invention of movable type, a person had to hand-carve the letters on blocks or stamps in order to make more than one copy of a document. The blocks were then dipped in ink and pressed onto textile or paper. Only the most important documents were duplicated. With the use of movable type, printing became a means of mass communication. Education (teaching, reading, and writing) became available to more people, and printing became the major weapon against mankind's greatest enemy - ignorance.
Small, "personal" laser printers are suitable for home use.
Inkjet printers are also popular for microcomputers. Less expensive than laser printers, inkjets produce higher resolution output than dot-matrix printers. Color inkjet printers are available at very reasonable prices.
A plotter, like a printer, produces hard-copy output. Plotters, which produce high quality color graphics, are generally categorized by whether they use pens or electrostatic charges to create images. Plotters are generally more expensive than printers, ranging from about $1,000 to $75,000 (or even more).
Storing printed reports requires a great deal of space. What can be done to save paper and storage space? Computer Output Microfilm/Microfiche (COM) provides an answer to the question.
Color graphics adapters are more expensive than monochrome, as they are color monitors. However, color is much easier on your eyes, and there are many programs that will not run without color. Increasingly, color is the standard.
Have you ever watched a television show on a computer? Audio output is a second type of soft copy. New computer systems have such good audio systems that it is possible to hear television through the computer's speakers. You can listen to music while you work, have the computer tell you when the printer needs paper, play games that include sound, or compose music on the computer.
Steady progress has been made in this area, though. The first systems could recognize only a few dozen words. A system recently released by IBM is capable of recognizing as many as 32,000 words.
Voice recognition has unlimited possibilities and will make computers much easier to use. Speech recognition systems are already being used. In factories, workers use these systems to control robotic arms when the worker's own hands are busy. Speech recognition systems also enable disabled people to use computers. A microcomputer Voice User Interface (VUI), capable of recognizing input from a variety of individuals, will be considered standard in the near future.
These printers are known as dot-matrix printers. If you use a magnifying glass to look at a report created with a dot-matrix printer, you can see the small dots forming each character.
Nonimpact printers are increasing in popularity. This fact is due largely to improvements in print quality coupled with decreasing cost. Some of the most popular nonimpact printers are laser printers and inkjet printers.
Laser printers work in the same manner as copy machines; a laser beam creates electrical charges that attract toner to form an image and transfer it to paper. Laser printers come in a variety of sizes, generally the larger and faster the printer, the more expensive it is. Large laser printers are used on mainframe computers where high-quality graphic output is required.
The printing press, however, did not make it easier for an individual to produce a document. Producing a document still required a pen or pencil. Then, in 1874, the company of E. Remington and Sons introduced the typewriter. A typewriter produced a document with characters of uniform size. Now a neater, more readable document could be produced more quickly.
The computer brought about tremendous changes. The first word processors were special-purpose machines designed solely to perform word processing. The special-purpose word processor included a typewriter or printer that produced top-quality printed material.
Later, word processing software was developed for use on general-purpose computers.
Sometimes, when watching television, you may notice that the picture looks a little snowy. This condition occurs because the images are not solid but are created by configurations of dots. These dots, or picture elements, combine to form the image you see. The more picture elements, also known as pixels, the better the resolution of the image. Computer monitors work in a similar way to a television screen.
The large monitors that you see connected to desktop computers are cathode-ray tube monitors (CRTs). The smaller monitors that are used on laptops and notebook computers are flat-screen monitors.
Sometimes it is advantageous to keep report files instead of paper documents because the files are easier to store.
Some programs create files that will be used as input to other programs. For example, an accounts payable program accepts a transaction file of all payments made in the last week, updates the master accounts payable file, and produces an accounts payable output file. The accounts payable output file is then used as input to the general ledger program. A backup file is a copy of a file, created as a safety precaution in case anything should happen to the original. Backing up data files regularly is extremely important. With any storage medium, the one thing you can be certain of is that it will fail - you just never know when.
|
