Apple IIgs - Manual (Page 12)

Page 12 of 84 II gs
Printed: Thursday, July 25, 2002 12:14:50 PM
For example, you might need to know that information isn't stored inside the computer as
letters and decimal numbers. It's stored as strings of 0's and 1's. Each letter, number, and
punctuation mark on the Apple IIgs keyboard has its own distinct arrangement of 0's and 1's.
The letter A, for example, is expressed as 1000001; B is 1000010.
The 0's and 1's are called bits. They're not really 0's and 1's; they're opposite conditions,
but it's more convenient to represent them as numbers. Even though it takes only seven bits to
represent each character on the keyboard, the computer allocates eight bits for each character.
The extra bit is sometimes used for error checking. A string of eight bits is called a byte.
The computer also uses 0's and 1's to do arithmetic. Whereas humans use a decimal numbering
system (based on the number of fingers on their hands), computers use a binary numbering system
(based on the two symbols they know how to manipulate: off/on or 0/1).
So, the computer processes information as 0's and 1's. It stores these 0's and 1's in RAM,
which stands for random-access memory. It's called random-access memory because the
microprocessor can go directly to any information it needs it doesn't have to access the
information sequentially the way you read a novel. The important thing to remember about RAM is
that anything you store there is temporary. When you turn off the power, everything in RAM is
erased that's why you have to remember to store documents on disks.
Do not confuse RAM with a similar acronym, ROM. ROM, which stands for read-only memory, is the
computer's permanent memory. It's called read-only memory because the micro-processor can read
and use what's on ROM chips, but it can't store anything there. ROM chips contain the
information that tells the computer what to do when you turn on the power, and other important
or indispensable information. That's all you need to know about ROM. RAM is of much more
interest to you because that's where the computer keeps track of the application you're working
with and the document you're working on. When this manual refers to memory, it's almost always
referring to RAM.
Chapter 3 - The Mouse and the Keyboard
Your Apple IIgs came with two important devices: a keyboard and a mouse. The keyboard is for
typing documents and for sending typed instructions to applications. The mouse is for drawing
pictures and for pointing to choices on the screen another way of sending instructions to
applications. The mouse and the keyboard are input devices; that is, they send information into
the computer.
How these devices work depends on the application so it' s up to the manual provided with the
application to tell you what you need to know to use the mouse and the keyboard with the
application. But the application may assume some familiarity with the special keys on the Apple
IIgs keyboard and with mouse terms like clicking, cutting, pasting, dragging, selecting, and
choosing from pull-down menus. If you have questions that aren't answered in the manual
provided with your application, come back to this chapter for clarification.
Applications written before the mouse came along accept only keyboard commands. More recent
applications usually give you a choice of using the mouse or the keyboard. These applications
are called mouse-based applications.
The first part of this chapter defines mouse terms and describes the standard user interface
for mouse-based applications. The second part of this chapter introduces the special keys on
the Apple IIgs keyboard and describes the standard user interface for keyboard-based
applications.
Some applications don't conform to the standard Apple II user interface described in this
chapter. This is especially true of older applications because they were written before a
standard existed. If you find yourself faced with an application that does things a little
differently, rely on the manual that came with the application for instructions on how to use