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These three pages contain a list of the terms you are most likely to run into when working on your Mac. If you don’t find a word here, check the index because I probably explained the term in the main body of the book. For an incredibly extensive and up-to-date resource of definitions, check www.webopedia.com (unfortunately, though, I don’t guarantee you will always understand the definition). Also check Sherlock (Chapter 31).

bits, bytes, kilobytes, megabytes, gigabytes

All of the terms listed to the left refer to size. It might refer to the size of a file, or how much space that file takes up on a disk. For instance, a small file like an icon might be 3K (kilobytes), and a large file like a high-quality photograph might be 15MB (megabytes). The layered Photoshop file for the cover of this book is 91MB.

Size might also refer to the size of your hard disk. For instance, you might have an 8GB (gigabtye) hard disk, or an 80GB hard disk. The bigger the disk, the more files it can hold.

bit: The smallest unit of information on a computer. Each bit is one electronic pulse. These are the ones and ohs you hear about, 1 and 0.

byte: 8 bits makes 1 byte. It takes one byte to produce one character, such as the letter A, on the monitor.

kilobyte: 1024 bytes makes 1 kilobyte (capital K). A page in a word processor might take about 6 to 12K of disk space, depending on how much formatting was involved.

kilobit: 1024 bits makes one kilobit (lowercase k). You’ll see this in references to Internet connection speeds. It is not the same as a kilobyte (capital K in abbreviations)!

megabyte: 1024 kilobytes makes 1 megabyte (MB). An 8-page newsletter with photographs and nice typography might take about 1.5 to 3MB of disk space, depending on how it was created. A software program like the one I am using to create this book (Adobe InDesign) takes about 90MB of disk space.

gigabyte: 1024 megabytes makes 1 gigabyte (GB). Most hard disks are now measured in gigabytes. The Mac I am using at the moment has a 75GB hard disk.


Disk refers to the hardware pieces that hold data. Inside your Mac you have an internal hard disk. You might buy an external hard disk that connects to your Mac through a cable. Removable disks are those that go in and out of a disk drive, which is the mechanism that “reads” the removable disk. Removable disks include floppy disks, Zips, CDs, DVDs, etc.

download, upload

Download means to copy files from one computer directly to another (as opposed to putting the files on a disk and carrying them to the other computer). Typically, the other computer is “remote,” or far away, and you download files from that computer to yours through the Internet. Upload means to copy files from your computer to a remote computer.


Hardware is hard—you can drop it, break it, and throw it. If you can bump into it, it’s hardware. Your computer is a piece of hardware, and so are external hard disks, scanners, modems, and printers. To send a piece of hardware to someone, you need a vehicle. Also see software.


Megahertz (MHz) refers to speed. In computers, the higher the megahertz, the faster the computer will process information. In 1993, a good computer had a speed of about 20MHz; today, even the cheapest computer is at least 400MHz, and more expensive machines reach a gigahertz. And every day they get faster and faster.

memory, RAM

Memory is the temporary storage place in your Mac, as opposed to the permanent storage space on a hard disk. There are various kinds of memory, but the one you’re most concerned with is random access memory (RAM). The more RAM you have, the better everything on your Mac will work. A minimum amount of RAM is 256MB; a great amount is a gigabyte or two. See page 138 to find out how much RAM you have in your Mac. You can always buy more RAM and install it—it’s easy.

operating system (OS) OS X is pronounced “oh ess ten”

The operating system (OS) is what runs the computer. It’s kind of like an engine in a car—you can have an entire car sitting in your front yard, but if it doesn’t have an engine, it’s not going to go anywhere. Operating systems get updated regularly so they can do more and more. You will probably get asked, “What OS are you running?” You’ll sound like you know what you’re talking about if you say, “Mac OS X version 10.2,” which is actually pronounced, “Mac oh ess ten point two.” Really.


Your monitor is composed of hundreds of thousands of tiny little spots; each one of these spots is a pixel. And each pixel is composed of three dots of light: red, green, and blue (RGB). The color in a pixel is a blend of varying amounts of those three colored lights. If all three colors are at 100 percent, the pixel is white. If no colors are sent to the pixel, it appears as black.


Software is invisible—it’s the programming code written on the disks. You buy software—the applications, utilities, fonts, and games you use—and it comes to you on some sort of disk, or you download the software from another computer to yours (like over the Internet). The disk it came on or the disk you are storing it on contains the software. You can accidentally destroy the software while the disk it’s on remains perfectly hard and whole. To send a piece of software to someone, you can use your modem and send it over the Internet.


Vaporware refers to software or hardware that has been promised for a while (“real soon now”) but hasn’t appeared on the market. You might also hear the terms wetware, liveware, or jellyware—that means us, the humans.

third party

Apple is the first party: they make the computer and the operating system. You are the second party; you use the computer and operating system. Other people who make things for you to use on your computer are the third party. This is a third-party book, as opposed to a manual straight from Apple.


A volume refers to any sort of disk or part of a disk. A disk can be separated into different partitions; each partition is still considered a separate volume. See Chapter 38 on how to divide your large hard disk into separate partitions.

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