OUTPUT: PRINTERS, NETWORKING,AND TRANSFERRING DATA

Printers

A number of things can happen to information after a user has finished working with it. In some cases, it may be enough to just see it on a monitor, or send it to a storage device. In most situations, however, it will probably be shared with other people.

The most common means of sharing computer information is to make a printed copy of it. While there are many brands of printers available in the marketplace, three kinds are generally available for personal computers: dot-matrix, letter quality, and nonimpact. The following comparison of these three kinds of printers originally appeared in Microcomputers for Insurance Professionals, written by Kenneth and Christina McClung, and John Guarneri

Dot-Matrix Printers

The dot-matrix printer gets its name from the way it produces characters. The print head has a set of wires that produce tiny dots according to a specific matrix pattern. For instance, an 8 x 9 dot- matrix printer produces dots in a matrix 8 dots wide by 9 dots high. The positioning of the dots determines the character formed. This method of printing is quick and inexpensive, but the quality of the characters produced is not as good as that of a letter-quality printer. (See Figure 22.)

A rule of thumb regarding dot-matrix printers is that the greater the number of dots in the matrix, the higher the quality of printed output: For example, a 9 x 23 matrix will produce higher quality print than will an 8 x 9 matrix. Some dot-matrix printers can approach letter quality by overprinting each character a second time with a light offset. This increase in the quality of appearance must be weighed against the reduction in output speed incurred by having each character printed twice.

  Figure 22. Dot matrix printer. Courtesy of International Business Machines.

The Letter-Quality Printer

The letter-quality printer produces the same high quality, fully formed characters as a typewriter. These printers give your correspondence a more professional appearance. In addition you can change the type style of your output with most letter-quality, printers. Letter-quality printers usually use removable typing elements available in most popular type styles. Depending on the brand of printer, this element may take the shape of a daisy wheel, a thimble, or the familiar IBM-style ball. (See Exhibit 6.)

Non impact Printers

Non impact printers are fast, quiet and generally the most expensive type of printers, with the cost often starting at $1,000. Some non impact printers also offer greater resolution and color graphics for users who need to produce sharp charts, reports and presentations. There are three kinds of non impact printers available: laser, ink-jet and thermal-transfer.

Laser: A laser printer uses a laser beam to write an image onto the photo conducting drum of a photocopier mechanism where the patterns pickup toner that is then transferred to a sheet of paper.

Ink-jet: Ink-jet printers spray ink at the paper at high speed, driving the ink into the surface with the impact.

Thermal-transfer: Thermal-transfer printers melt an image onto the paper by using precision heating elements and either a thermal ribbon or a transfer sheet.

 

 EXHIBIT 6. Comparison of text created by different types of printers. Reprinted with permission from Microcomputers for Insurance Professionals, McCluny, Guerriesi, and McCluny, John Wiley and Sons, 1984.

 

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Records and files OF Programs

Computers store and process information in records and flies (see Figure 19). A record is a collection of related items that are stored in memory. A file is a collection of related records that are treated as a single unit. For example, you have sent a group of letters to a company called Jim’s Shoes and PC Emporium. Within the computer, the file becomes “Jim’s Shoes.” Each letter sent (and stored) represents one record of that file, as can be seen in Figure 20.

When you create a file, you may tall it almost anything you like, as long as it does not exceed eight characters in length. There

 

FIGURE 19. Computers manage data much the same as you handle files. Drawing courtesy of International Business Machines.

FIGURE 20. Drawing by Gina Bean.

are, however, certain characters that cannot be used in file names because the operating system reserves them to refer to system components. These include:

CON

AUX

COMI

LPT1

PRN

NUL

A complete list of all file names in either the program you are using, or the files you create, are available in a directory. A directory shows the file name, how much space (in bytes) it takes up. And the date it was created. Diskettes are capable of holding up 1e 112 files each.

When setting tip a file, try to make the file name as descriptive of a file's contents as the eight character limitation will allow (see Figiure28).

EXAMPLES OF FILE NAMES

Good                                                                                           Bad

Inventory                                                     Inventory (has more than eight characters)

Table                                                             (contains a space that isn’t allowed)

 

FIGURE 21. Courtesy of International Business Machines.

File name extensions

A file name extension is a brief three-character addition to a file name used to help identify or categorize the type of file it is. Extensions appear after the file name and are separated from them by a (.). One example might be book.fic, which would identify a series of sub files within the main file. In this case, the primary file identifies books, and the file name extension further breaks that down to works of fiction.

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Programming Languages

As noted earlier, computers work only with binary information. This machine language is really nothing more than a series of Os and Is strung together. Machine language, however, is a difficult way for most people to communicate with a computer. To simplify things, a number of high-level programming languages were created. These are much simpler to use and understand because of their similarity to the everyday language of human communications. These programming languages are translated into a code the computer understands, using the firmware installed in it by the manufacturer.

Among the most widely used languages are:

FORTRAN: (Formula Translator). It is used primarily in medical, scientific, and technical applications.

COBOL: (Common Business Oriented Language). It is one of the most popular business and accounting languages.

BASIC: (Beginners All Purpose Symbolic Instruction Code). This is as close to English as current programming languages come. BASIC is supplied with many personal computers, by the manufacturers.

PASCAL: (Named for the Seventeenth-Century French Mathematician Blaise Pascal). This is a popular programming language with many microcomputer users, who consider it easy to learn.

No matter which language a program is written in, the languages generally share four fundamental activities. They:

1. Provide a method for getting something into the computer, and getting it out again

2. Make comparisons

3. Decide what activities need to be performed

4. Repeat tasks until a particular job is completed

With the wide variety of software packages on the market that meet the needs of most users, it is probably not as important to learn a programming language as it once was for the average user.

 

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PROGRAMS

All the activities a computer performs are guided by a program. A program is  simply a set of instructions or commands that tells

 FIGURE 17. A personal computer with a 10 megabyte hard disk can store the equivalent of 3333 pages of text.

FIGURE 18. Three types of computer memory and storage devices. A microchip (64K). Diskette (320K) and hard disk (10 megabytes +). 

The computer how to perform a specific job. You may write your own programs using a programming language, or by purchasing a preprogrammed software package. Such packages will do spreadsheets, word processing, database management, communications, tax preparation, inventory, project management, games, household budgets, and hundreds of other tasks. While a person working with a personal computer might only make a single entry, like entering an amount into a checkbook register, the program that pulls everything together into something meaningful might actually have several steps. From the computer’s point of view, the program of instructions might look something like this:

I - Take the contents of memory location 5.

2. Add this to the contents of memory location 15.

3 Compare this to the contents of memory location 17.

4. If the contents are the same, store the results in memory location 21.

5. If the contents are not the same input a warning to the system monitors.

Programming languages

As noted earlier, computers work only with binary information. This machine language is really nothing more than a series of Os and Is strung together. Machine language, however, is a difficult way for most people to communicate with a computer. To simplify things, a number of high-level programming languages were created. These are much simpler to use and understand because of their similarity to the everyday language of human communications. These programming languages are translated into a code the computer understands, using the firmware installed in it by the manufacturer.

Among the most widely used languages are:

FORTRAN: (Formula Translator). It is used primarily in medical, scientific, and technical applications.

COBOL: (Common Business Oriented Language). It is one of the most popular business and accounting languages.

BASIC: (Beginners All Purpose Symbolic Instruction Code). This is as close to English as current programming languages come. BASIC is supplied with many personal computers, by the manufacturers.

PASCAL: (Named for the Seventeenth-Century French Mathematician Blaise Pascal). This is a popular programming language with many microcomputer users, who consider it easy to learn.

No matter which language a program is written in, the languages generally share four fundamental activities. They:

1. Provide a method for getting something into the computer, and getting it out again

2. Make comparisons

3. Decide what activities need to be performed

4. Repeat tasks until a particular job is completed

With the wide variety of software packages on the market that meet the needs of most users, it is probably not as important to learn a programming language as it once was for the average user.

 

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A QUICK REVIEW ON COMPUTERS COMPONENTS

One very simple way of thinking about how computers work is to make a comparison between a personal computer’s components and corresponding human functions:

  PC Components                               Human Functions

)    CPU)                                                       Brain

   Memory                                           Ability to recall things

Software                                                  Intelligence

Input (i.e.: keyboard)                            Five senses

Output (i.e.: printer)                            Speech, writing

Unlike humans, computers need to be told exactly what to do before they will perform any task. Computers also work only with binary (numeric) information. In order to perform, a computer first converts all programs and data into this numeric form that it can understand. Once this is done, it will perform any task assigned it. All of these activities are accomplished by the operating system. Essentially, the operating system is a group of programs that have the responsibility of telling the computer what to do, and the most efficient way of doing it. The operating system for IBM personal computers and IBM compatible systems is the Disk Operating System (DOS), which performs a number of jobs that can be broken down into three main functions:

1. Handles and manages files

2. Oversees the use of operating hardware

3. Interprets and executes commands (see Figure 15)

Memory and storage

While humans think of memory in terms of words or amounts of information that can be remembered, computers think of memory in terms of bits, bytes, K, and megabytes. The smallest unit of memory is the bit. A bit is a binary digit of information. Eight hits equal one byte, which is considered the standard unit for computing information. While the bit is too small a unit of information to spend much time worrying about, a byte can be thought of as one character, such as a letter, number, symbol, or space. For example, the phrase: “Tom, come here” contains 17 characters (4 symbols, 11 letters, and 2 spaces). This means the phrase also has 17 bytes. The symbol K represents 1000 bytes (1024 to be precise). A megabyte (Meg) contains one million bytes. One way to think about this is to compare it to a standard page of typed text that contains around 3000 characters, or 3K of information. Using this analogy, one megabyte would be roughly equal to 333 pages.

FIGURE 15. The disk operating system is an indispensable part of a personal computer, governing everything from file management to the hardware.

Obviously, the more memory capacity a personal computer has, the more it can accomplish. A 5.25-inch double-sided diskette, for example, can provide over 320K of long-term memory (or about 107 pages of standard text). (See Figure 16.) Many personal computers have hard disk memories, designed to hold 10 megabytes (see Figure 17) (about 3333 pages of equivalent text) or more. Diskettes and hard disks (sometimes called Winchester disks) allow for the long-term storage of programs or data. Unlike the

FIGURE 16. A diskette can hold the equivalent of 107 pages of text.

Internal working memory, the information stored in these outside sources isn’t lost when a computer is shut off. Both sources also offer mass storage capabilities that the computer’s internal memory isn’t large enough to deal with. Other types of storage devices include cassette tapes (which are rarely found in business systems), cartridge tape systems, which can be plugged directly into the personal computer or be kept as a separate piece of equipment, external hard disks (sometimes called expansion units) connected to the system but physicality separate from it, mass storage devices designed to support several systems, and hard disks that can be plugged directly into .1 personal computer (Figure 18) and then removed to be stored elsewhere.

 

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TYPES OF MEMORY STORED WITHIN A SYSTEM

There are two types of memory stored within a system:

1. Read Only Memory (ROM)

2. Random Access Memory (RAM)

Read Only Memory is permanently imprinted in your computer when you get it. It is called ROM because it is meant to be read only by the computer itself. The person operating the computer has no control over it. The computer uses this memory to tell itself how to start up when you turn it on. Read Only Memory processes the electrical data flow from the keyboard to the CPU and from the CPU to the video display screen or to any other peripheral equipment you have attached, such as a printer. The decoders that translate numbers and characters into binary information that the computer understands are found in ROM. These programs are called firmware, or nonvolatile, because they are always there, and are not erased or destroyed when the power is turned off.

The other memory a system works with is called, Random Access Memory (RAM). This is what some people also call Read/ Write Memory, and is considered volatile because the information stored here is lost whenever the computer is shut off, or when power is lost. Random Access Memory is controlled by the person working with a system, and is where the instructions and information needed to get a job done are temporarily stored. Personal computer systems are often described by the amount of short- term (RAM) memory available (i.e., 64K, 256K, 640K). Most software programs also list the amount of memory they require to be stored in RAM. Most systems allow the user to increase the amount of memory available by installing additional single memory chips or expansion boards containing multiple chips. Even with these, however, there are finite limits to the amount of memory a personal computer has to work with. This is one reason why it is important to decide what kinds of work you would like to perform on a personal computer and the software most appropriate for accomplishing those tasks, before you purchase the system. This allows a computer to be configured to meet anticipated uses and eliminates the problem that a lot of people encounter of trying to install a software program that requires more memory than their system has available. In these situations the only recourse is to purchase and install more memory. A person using a computer comes in contact with all of its working parts. When a system is first turned on, the operating system takes over and makes sure everything under its control is functioning properly. Information is put into the system, where it is stored in memory according to an address code assigned by the computer, as seen in Figure 14. When the program (or list of instructions) is loaded, data are taken from the memory. Following the program instructions, the

FIGURE 14.  The flow of information processing. Illustration by Gina Bean. Data are then worked on in the Arithmetic Logic Unit (ALU). When all the instructions have been carried out, the information is returned to memory or to an output device.

Output can be delivered through any of several sources:

.Video Monitor (CRT)

.Printer

.Voice synthesizer

.Modem for transferring information over telephone lines

.Storage device (diskette, hard disk, etc.)

 

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HOW A COMPUTER OPERATES

What goes on inside a computer is a mystery to most people, and even a little frightening to some. Actually, it is a fairly simple process - Whether we are talking about a supercomputer or one that can sit on top of a desk, all function in the same general way.

To understand how computers operate, we first have to break them down into several basic elements:

1. Input

2. Central processing unit (CPU)

3. Memory or storage

4. Output

Information is put into the computer through any of several different sources:

1. Keyboard

2. Data diskette (which can contain the program of instructions

What Are The Components Of A Personal Computer

The hardware components (those things you can see and touch), for a personal computer include:

A microprocessor (or system unit)—This is the Central Processing Unit (CPU) for a personal computer. While it looks like a box, it contains the memory systems (RAM and ROM) and is really the heart of the system. This unit also contains the disk drives. Since the memory is wiped clean each time you turn the machine off, you need a more permanent storage system. This is provided by keeping separate memory diskettes.

• A keyboard that lets you communicate with the system.

• A video display monitor (like a TV screen) that lets the system communicate with you.

• A printer that can produce a paper copy of whatever you are working on.

Diskettes—The software containing the programs you wish to run or on which to plan your work. A diskette is a small magnetic record that contains the storage space for your memory. When a diskette is inserted into a disk drive, it is spun much like a record on a turntable, and “read” electronically. A single sided diskette can hold the same amount of information as 110 pages of single-spaced text.

You will be working with, or the information you will be working on)

1. Cassette tape

2. Graphic tablets and electronic pens

3. Light pens, which can be used by directly touching the screen of a monitor

One key point to remember is that a computer will do exactly as it is told, and only what it is told. This can lead to what programmers call GIGO or Garbage In, Garbage Out. If the user doesn’t give the computer the correct information to work with, and precise’ instructions on what to do with that information, he or she will get back incorrect or meaningless answers and results.

Data is entered into the CPU. The CPU is where all the logical and control functions of a computer are carried out. The CPU is actually divided into two areas: a control unit, and the arithmetic and logic unit (ALU). The control unit spends its time figuring out what the computer is supposed to do next, and the ALU actually does it.

Memory is where information and instructions are stored. How does a computer memorize? A series of on/off switches lead an electrical current to a particular location, or address. Information is moved between the CPU and its memory banks by electronic pathways or conduits, called registers.

 

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