The Digital Research Initiative
The University of North Carolina at Chapel Hill

Computer Concepts:

Taking the Mystery Out of the Machine

Quite a few people tell me that they hate computers. Here's a list of things that may help you to become computer-smart.

1.) What is a Computer? And what is computer software?

The computer is an electronic device or a programmable electronic machine that performs high-speed mathematical or logical operations or that assembles, stores, correlates, or otherwise processes information (usually in a binary form) according to instructions given to it in a variable program. [Yow! Where did that technical-sounding definition come from? Shouldn't we quote a source for it?]

Computer software is a program or coded set of instructions that tells a computer how to do things. You might say software tells the computer how to think. Here's another technical sounding definition we found somewhere: "Software is written or printed data in the form of programs, routines, and symbolic languages, essential to the operation, maintenance of computers, functioning of the hardware and directing its operation.

These are coded instructions that tell a computer what to do, ranging from composing a spreadsheet for a quarterly report, to creating a database for managing huge inventories, or making it possible to use a notebook computer to write letters, or, in the case of cellular phones, instructing the telephone how to interact with the transmitters.

Software is in fact, formless, intangible, invisible and invisualizable, and could generate invaluable riches. Bob disagrees with the "written or printed data" part of this definition. Sure, any piece of software *was* written by someone (or was created by a program that was written by someone), but when you get it it's either on a disk or on a chip or just floating through the Net and your computer as electricity. Bob usually thinks of software as *instructions* and data as the stuff the instructions tell the computer to act *upon.* But Webster includes "data" in the definition of software, and that should include digital images, text, sounds and other stuff.

The main distinction you should know is that hardware is touchable and software is not. So saying it is "written or printed" is misleading.

2.) What is a Software Application?

It's a computer program that does some kind of task, such as word processing or calculating your income taxes. Perhaps computer games are a kind of application, but most often the term is used for work-related programs. Besides "application software" there is "system software," which makes the computer work, such as Microsoft Windows or UNIX or the Macintosh System and Finder. Some application programs that make the computer work more efficiently or perform housekeeping tasks are called "utility programs" and fall somewhere in between the broader "application" and "system" categories.

3.) What is Computer Hardware?

Computer Hardware is stuff you can hit, kick, or drop on your toe: the computer monitor, keyboard, mouse, etc. Some hardware is inside other hardware; you can add extra video circuit boards to the computer, for instance. Our Macintosh in Manning even has a circuit board with a PC processor, so it is two computers in one.

4.) I am confused. What's an operating system in a computer? What's Windows 95? Does it have any relation to a Macintosh?

A computer's operating system is the basic software that enables the running of other computer programs. The major operating systems are Microsoft's DOS [stands for Disk Operating System] and Windows, the Macintosh OS and Unix.

Windows 95 is an updated version of the Microsoft's previous DOS system and Windows, which you could think of as two layers of operating systems. DOS, Windows and Windows95 run on computers built by IBM, Compaq, Gateway and other companies using Intel or Intel-inspired processing chips. Windows and Windows 95 were inspired by the Macintosh OS, which first came out in 1984 as the system for people who thought Microsoft's DOS was ugly and hard to learn.

Today, the latest version of the Macintosh OS is still an easy to use operating system; one popular Mac-user joke calls the Mac OS "Windows'84," since Windows '95 finally offered some features the Macintosh has had all along.

5.) What is UNIX? Do we need to know UNIX?

Unix is an extremely popular, usually cryptic, operating system in wide use on computers on the Internet. Other operating systems work fine on the Internet, but Unix is probably the most common.

UNIX was created by AT&T's Bell Laboratories before personal computers were invented. It started out on large computers that served dozens of people at a time using "dumb" terminals that were not computers in themselves, like the terminals used for the Davis Library catalog. UNIX, unlike DOS, was designed to do more than one thing at a time, which is called "multitasking." Windows and the earlier Macintosh were designed to switch between tasks quickly to give the illusion of doing more than one thing at a time. The latest Macs and PC chips are finally powerful enough to do "true multitasking."

As of Spring 1996, we have Macintosh programs that let us use the UNIX computers on campus without actually knowing many UNIX commands. But since your email account is on a UNIX computer you should take the time to learn enough about it to protect the privacy of your mail -- and to let other people see the Web pages you'll create later in the semester.

6.) What is the difference between a Macintosh and a DOS computer?

Until recently all Macintoshes were built by Apple Computer Co., and they were the first popular computers to use a mouse and a "graphical user interface," GUI for short. That means the Macintosh can use pictures of a disk or a file folder to represent your disk and its contents. The Macintosh's main chip is made by Motorola, and the main operating system is made by Apple.

DOS computers include the original IBM PC and all the copies (or "clones") and improvements by IBM and other companies -- Compaq, Packard Bell, Hewlett Packard, Toshiba and hundreds of others. The main chip is made by Intel, or by companies that copied Intel's basic designs. The DOS operating system is made by Microsoft. (It stands for "Disk Operating System" to differentiate from older operating systems that used tapes.) The same Intel-based computer can run UNIX or other operating systems, but Microsoft has contracted to have DOS sold with almost all new PCs, making it an "industry standard."

The Macintosh was so easy to use that Microsoft came up with its own GUI interface, called Microsoft Windows. Now it, too, is sold with most new PCs. The new version, Windows 95, has major improvements, but some are things the Macintosh has had since 1985 -- so don't feel you're being left out by using a Mac lab!

7.) Can a Mac read PC disks?

Sometimes. The early PCs used 5 1/4 inch disks that didn't fit the Mac. The newer PCs use the same 3 1/2 inch disks but they store information differently. That is, the "disk format" is different.

8.) What's a disk format?

Think of disk formats as the lines on notebook paper. One company puts out a notebook with narrow lines, another with wide lines. The disk drive is like an automatic pen designed to write on only one kind of notebook. If the "lines" aren't where the computer expects, it might think the disk is blank when it really isn't. Physically, the IBM and Mac disks are the same. You "put the lines on" by "initializing" or "formatting" the disk.

Some of the newer Macintoshes (including the Power PC at the front of the JOMC Mac lab) have a program that automatically recognizes a PC disk and can read from it or write on it. Most of the Macs in UNC labs now have that program, so you can use PC-formatted disks in them. However, if you put a PC-formatted disk in an older Mac that will not read it, don't let it trick you into re-initializing your disk as a Mac disk; the information from the PC will be erased and the PC won't be able to read anything you store on it with a Mac!

9.) What is a Modem? Where does the word come from?

"Modem" is short for "Modulator-Demodulator." It's the device that connects a computer to a telephone line. It "modulates" digital signals from the computer into analog sound waves for the telephone, and it demodulates the telephone's sounds into digital information again. Most of today's modems also have circuits to let them talk to fax machines, and come with fax software letting you "print" from your computer programs right into the fax modem and out the other end on someone's fax machine. Their speed is measured in "bits per second" (bps), and 14,400 bps seems to be the latest standard, but 2400 bps can be tolerable for simple text like email.

In other words, the modem is a device that converts data from one form into another, as from one form usable in data processing to another form usable in telephonic transmission. Also called data set.

10.) My friend has a computer with a Pentium chip. What is a chip? Also what's a microprocessor?

The chip is a minute slice of a semiconducting material, such as silicon or germanium, doped and otherwise processed to have specified electrical characteristics, especially before it is developed into an electronic component or integrated circuit. Also called "microchip."

A microprocessor is an integrated circuit that contains the entire central processing unit of a computer on a single chip.

11.) What is the main brain of computer?

The main brain of the computer is the processor chip. Chips have a speed measured in megahertz. The faster your chip is the faster everything will work in your computer. DOS PCs have evolved through several generations of Intel processors with numerical names, from the 8088 to 80286, 80386, 80486 and (because Intel learned these numbers couldn't be copyrighted) the Pentium. Each processor can be made at different speeds, so you can find a 50, 60 or 100 mHz Pentium.

The Macintosh originally used Motorola chips with numbers starting with 680 (e.g., 68000, 68030, or 680LC40), but more recently IBM, Apple and Motorola decided to create a whole new chip, called the Power PC chip, which competes with the Pentium for power and speed. What's all this power for? If you're not crunching big scientific numbers, it's mostly useful for handling pictures and sound, and for running very big, complicated programs like Microsoft Office or Photoshop. If you just wanted to put words on the screen or check your email, a 1984 PC or Macintosh would be just fine. And it would cost less than the Modem! (But its old software might not be as easy to learn as the new stuff.)

12.) What is a CPU?(HINT: -- there are two correct answers, so give both)

CPU means Central Processing Unit. Sometimes that means the big box on the desk with the keyboard, monitor and mouse plugged in. Other times it means the main computer chip inside the box. That chip can be called "the processor" too. It actually does the "computing" that does all the magic. The Central Processing Unit of a Computer is its main chip. It's also the name given to the box containing that chip and lots of other chips and circuit boards that speed things up, store information, or perform special functions. The case also can hold disk drives, and it has sockets on the back called "ports" to plug in other drives or devices, including keyboards, mice, printers, modems, and other computers.

13.) What do RAM, ROM and one of the CPU definitions have in common?

They're all chips. Random Access Memory (RAM) chips are the "working memory" of the computer. The CPU can put information anywhere on those chips ("at random") as long as there's electricity. Most office computers these days have somewhere between 4 and 3 2 megabytes (MB) of RAM.

More expensive computers, including scientific "workstations" and "mainframe" computers have more. ROM chips are Read Only Memory, which means you and your computer cannot change the information stored on them. Computer manufacturers use ROM chips to store part of the basic operating instructions for the computer. Enough of the operating system of a computer is "in ROM" to tell the CPU how to get the rest of the operating system from the disk, turn on the screen, and wait for you to use the keyboard or mouse.

14.) What's the advantage of a CD-ROM Drive?

CD-ROMs store programs, databases or documents just like hard drives and disks, but they do it using laser-optical technology. They are "written" at the factory and can't be erased or written on by your computer, just like the difference between music CDs and cassette tapes. CD-ROM drives were originally slower than hard disks, but they are also getting faster, so you'll see "double speed" and "quad speed" mentioned.

A single CD-ROM can store about 800MB, enough for a encyclopedia or a combination of text, pictures, sound and video, which is why you now hear so much about "multimedia" applications. Sound and video take a lot of room, which is why a CD can hold one symphony, or the printed scores and pictures of the composers for many symphonies. All of the known literature of ancient Greece is available on one CD, called Perseus, and they had room left over for lots of still pictures.

And the same CD-ROM Drive usually can play your music CDs.

15.) What do ROM and CD-ROM have in common?

A CD-ROM obviously is a disc, not a chip. But for now these high-capacity optical storage discs are "written" at the factory and your computer can only read them. But user-writable optical disc drives, using slightly different technology, are starting to be affordable (at least for those who can afford them!).

16.) What is a Disk Drive?

A computer disk is a circle of plastic or metal covered with a magnetic coating, a lot like a cassette tape's surface. The plastic ones used to be called "floppy disks" because they were obviously flexible. (Even today's hard plastic 3 1/2-inch disks have a floppy disk of plastic inside.) The metal ones are called "hard disks" or "hard drives" and store a lot more information. The disk and its drive mechanism are sealed in a case together to keep out dust -- even a particle of cigarette smoke could jam the tiny space between the disk and the "head" that reads and records information. Disk manufacturers keep figuring out how to get more information in a smaller space at a lower cost.

17.) What are "bits"? I've seen the measures "8 bit," "16 bit" and "32 bit" in ads and articles about computer chips and video display cards. What's that all about? What is the difference?

The term bit or bits comes from combining the words BInary and digIT. In computing, a bit is a unit of information expressed as a choice between two possibilities: a 0 or 1 in binary notation. (Binary is the coding system using the binary digits 0 and 1 to represent a letter, digit or other character in a computer).

This has to do with how many bits the CPU (or a video processor) can handle at a time. That can translate into faster CPUs, the ability to do more things at once, and the detail (or number of colors) on the screen.

18.) A computers magazine is named"Bits and bytes." What are bytes? What are kilobytes, megabytes and gigabytes?

A byte is a the amount of computer memory needed to store one character of a specified size, usually 8 bits for a microcomputer and 16 bits for a larger computer.

Starting almost at the bottom, a byte is the amount of computer storage or memory needed to hold roughly one typewriter character. The computer does this using binary numbers, which you don't need to know about in this course. And it actually uses eight BInary digiTs (bits) to represent each byte.

The rest of the terminology is roughly metric (but really representing powers of two), and it's close enough to think of 1K (kilobyte) as 1000 bytes (it's really 2 to the 10th power, or 1,024), a megabyte as a million, and a gigabyte as a thousand million bytes. Using a special compression program to filter out duplicated words and letters, you can squeeze a copy of Moby Dick into less than 600K. Dickens's "Christmas Carol," with no fancy compression, is about 176K.

19.) What are megabytes?

Information on a computer is measured in "byte." A byte is roughly the space needed to store a character. A pocket-size computer disk stores 1.44 million bytes, or megabytes (or MB for short). Early PC hard disks stored 10MB and were 10-pound blocks of metal the size of two building bricks. Today a Mac Powerbook can have a 240MB hard drive inside that's about the size of a pack of cigarettes. Some of today's programs take up 40 to 60 MB all by themselves, before you've written a word or painted a picture. You can never have too much disk space, but you can probably survive with 80MB.

20.) We measure driving speed in miles per hour. How is a computer's speed of operation measured? What units do we use?

A computer's speed is measured in megahertz. The speed of a processor chip in a computer is measured in frequency the unit of which is megahertz (faster is better); For example, a chip with a 100 megahertz calculates faster than my computer's 60 mHz chip. And "calculates" includes operations like painting a big picture on the screen, one bit at a time. "Mega" means "million" and Hertz (named for the 19th century German physicist H. R. Hertz who detected radio waves [Abbreviation: Hz]) is a unit of frequency equal to one cycle per second. So, a megahertz is one million cycles per second.

21.) What do you mean by computer memory? Susan recently bought a Power Macintosh with 16 megabytes of RAM and 500 megabytes of hard disk space? What's RAM and what's hard disk space?

In computing, the memory of a computer represents its capacity to preserve data for retrieval and capacity for storing information. The two kinds of memory specification you will look for in a computer are RAM and hard disk space.

RAM stands for Random Access Memory. Any software program when launched resides in this space. The unit of RAM is megabytes and the RAM space limits how many software programs I can run at the same time.

The Hard Disk space is also measured in Megabytes. So when we say Susan's Power Macintosh has 500 megabytes of hard disk space we are describing the storage capacity of the hard disk.

22.) How much RAM should my computer have?

RAM defines the memory of a computer. It is measured in megabytes or MB for short. The more RAM you have the more you can do with a computer. For instance you can run several complex programs and run them all at once. Today, 4 MB of RAM is generally the minimum sold with a computer, but 8 MB is probably the minimum you need to run basic applications. The computer has sockets inside to hold more RAM chips, so you'll see ads that say something like "4 MB RAM, expandable to 36 MB." Some ads for laptops may not mention that there's no room inside for more memory, or only for a maximum of 8 or 12 MB.

23.) I tried to check my Email and the computer said "insufficient memory." Does that mean my disk is full? Or does it mean that the hard disk is full? Otherwise, what *does* it mean? And what can I do about it?

Try not to think of disks as "memory." Think of them as "storage." "Memory" in this case means Random Access Memory (RAM), the temporary, electricity-dependent memory of the computer chips. If the computer's memory is insufficient to run TELNET or some other program, it's probably because some of the memory is being used by other programs. So the solution is to close one or more of the programs you're running. (To really increase the memory, you have to buy and install more chips, usually in groups called Single Inline Memory Modules (SIMMs for short). That's expensive and you have to turn off the computer to do it.)

24.) What is an upgrade? Most of today's computers can be "upgraded." That is, you can add more RAM, bigger disk drives, CD-ROM players, modems, faster video cards, a prettier mouse, or a card that turns the PC into a color television. You can also add some devices outside the computer, through its "ports" or sockets, such as an "external" modem or drive, a printer, a scanner, or a joystick to play games.

25.) John is typing a letter on his computer. While writing the first paragraph, he accidentally kicks out the power plug and the computer goes blank? Where *IS* that paragraph right now?

Unless John saved his first paragraph, the words he typed on his computer are only electrical voltage right now, flickering through the memory chips inside the computer. When you save this on a disk, you convert the electrical impulses to positive and negative points on the disk's thin magnetic coating.

26.) What is "the Desktop"?

The Desktop is the Mac's cute name for the screen you see when you first turn on the computer. While the computer is starting, the bottom edge of the Desktop will show symbols representing any programs designed to load automatically at start-up time. When things settle down, the Desktop shows the trash can, any available disks, and any folders or windows left open for easier access, as well as the menus at the top of the screen, headed File, Edit, View, Label, and Special. Looks just like MY desk...

27.) What are "the Finder" and "the System"? What is "Windows"?

The System is the main operating program for the Macintosh. It's the first thing to load automatically. The Finder is the program that shows you the Desktop, your folders, windows, and everything.

28.) What is a Mouse?

The mouse gives you the point and click simplicity that helps make computers easy to use.

29.) What is a mother board? That's the main circuit board in the computer, the one with the CPU chip and the sockets for everything else.

30.) What's a Sound Board? Macintoshes have some sound capability built in; PCs originally didn't, but had a small speaker that could beep and squawk. Sound boards give the computer higher qualities of sound, including high-quality digital stereo. Then you can add speakers, and a microphone to record your own voice.

31.) I know you can see a computer screen on a monitor. What should I look for in a monitor? Monitors are measured diagonally, including the case. The standard PC or Mac monitor these days is a 14-inch or 15-inch monitor. The displays (and their video cards) vary in the size of the pixels (dots) making up the image. Smaller dots are better, so a ".26-mm dot pitch" is better than ".30" and anything bigger than .30-mm is probably hard on your eyes. The video card and its memory (1 MB, 2 MB or more) determine how much detail and how many colors it can put on the screen. For example, one Sony Trinitron RGB Color Display "delivers unmatched image resolution and clarity in 32,768 colors with built-in video support; 640 by 480 pixels; .26-mm dot pitch for high-resolution, flicker-free text and graphics."

32.) What is a "server"?

A server is a computer running software that presents programs or information to other computers. (The other computers are sometimes called "clients" of the server.) The Mac lab has a file server at the front of the room with a hard disk called "Graphics Basket." That shared disk should be represented on each Mac's screen as a subtle little cartoon of a serving tray with files on it and wires dangling from the bottom. "File server," get it? Macs are big on "cute."

33.) What's a network?

When you connect a group of computers together, you have a network. If one of the computers is set up so that all of the others can read its hard disk or receive information from the central source, that computer is a "server" and the others are "clients." A small network of office computers is called a Local Area Network or LAN. Larger networks are called "Wide Area Networks," such as the campus network used for email. The Internet is the global network of other networks.

34.) What is "text only"? Is it like ASCII? OK, what's ASCII?

Most word processors store documents in a proprietary "file format" designed by the program's manufacturer, with its own special codes for handling footnotes, underlining, font changes, margins and other fancy features. If you stripped out all that extra information, leaving only the characters you see printed on the typewriter keyboard, you would have a "text only" or "plain text" document.

In the PC and UNIX worlds, this is usually called an ASCII file. ASCII (pronounced "asskey")is short for American Standard Code for Information Interchange, so that's not a Roman numeral at the end. And as the name suggests, ASCII or "text only" files are the easiest way to move information from one kind of computer to another Ü including from the Macs to a PC or a UNIX machine like ISIS, the Email server.

35.) Will we have any need for ASCII?

When we create pages for the World Wide Web, we'll be using ASCII files. One last difference between PCs and Macintoshes, by the way. The ASCII code was written in the days of unsophisticated teletype machines that printed on paper as you typed. When you got to the end of a line, one code returned the printing "carriage" to the left, another code advanced the paper.

PCs use both these invisible codes, Carriage Return (CR) and "Line Feed (LF) to mark the end of a line of text. The Macintosh uses only one of them. So if you open an ASCII file from a PC with a Macintosh, you may have a meaningless little rectangle at the start of each line, representing the unneeded code. Some Macintosh editors automatically filter out those characters, others leave you to delete them yourself.

Macintoshes also use some non-ASCII characters, including "smart quotes," a single ellipsis character (displayed as three dots), a bullet character and perhaps a few others that will not appear as intended when transferred to a PC or UNIX computer.

Since a Macintosh or Windows computer can cut (or copy) and paste between application windows, it's easy to copy small passages between your Telnet sessions and a text editor, as long as you don't paste any of those Mac-specific characters. (Note: That means you can write your Email or text for your Web pages "offline" while ISIS is busy, then paste it into ISIS's mail or editing programs when you finally get connected.)

36.) What are Pine and PICO?

Pine is the Email program on ISIS and many other UNIX computers. PICO is a text editing program. Neat transition from the last question, huh? PICO's commands are the same ones you use to write Pine mail, but you can also use PICO to write documents, including Web pages, and store them on your ISIS disk space.

By the way, ISIS was originally two computers working together and its name was a cute abbreviation for "Information Systems" doubled, if I remember my local folklore correctly. But being the name of an Egyptian goddess is a nice touch. Later, you'll learn about Ra. Computer users at UNC sometimes refer almost interchangeably to "ISIS" or "the email server" or just "email." The university from time to time installs a new computer to manage email but gives that new computer the "alias" address of "email.unc.edu" to keep from confusing everyone who sends mail to or from the university.

37) When was the first computer invented? Who is credited with having conceived the first digital computer?

The first automatic digital computer was conceived in the 1830s by the English inventor Charles Babbage. Called the analytical engine, Babbage's plans embodied most of the basic elements of the modern digital computer. However, the analytical engine was never completed. Babbage's invention was forgotten until his writings were discovered in 1937.

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