These include a 10 key (0-9) numeric keypad and the
cursor control keys. Also, beginning on the top row at
the right, you see the NUM(eric) LOCK key, SCROLL
LOCK key, PAUSE key, and the PRT SC (print screen)
key. Located on the bottom right-hand side of the
keyboard are the INS(ert) and DEL(ete) keys. The
purpose/function of each of these keys is as follows:
FUNCTION KEYS F1-F12 These special-
purpose keys are used to communicate special
functions to the operating system, such as MS-
DOS, or to applications software. The meaning
of each is defined by the particular software.
This simplifies tasks that might otherwise
require several keystrokes. These keys can also
be used with other keys to increase the number of
functions you can specify to a program.
NUMERIC KEYPAD KEYS To activate the
numeric keypad, press the NUM LOCK key.
The NUM LOCK key may contain an indicator
light within the key to indicate when it is ON.
Use the numeric keypad just like a calculator
keypad to enter numbers you will be using in
mathematical functions.
CURSOR CONTROL KEYS The CURSOR
CONTROL keys are most important. They
allow you to move the cursor from one place to
another on the display screen. Remember, the
cursor is the indicator, the spot of light on the
screen, which lets the user know where the next
entry will be made. On the keyboard shown in
figure 1-17, the cursor control keys are located in
two locations, both on the numeric keypad and as
a separate keypad. When the NUM LOCK key is
OFF, you can use the arrows on keys 2,4,6, and
8 to control cursor movement one line up or
down, or one position to the left or right, as
shown by the direction of the arrow. The
remaining cursor control keys on keys 1, 3, 7,
and 9 are used to move the cursor to other parts of
the screen or document/data (for example, the
end of a line [END key] or the top of the next
page [PgDn key]). Some software packages use
the cursor control keys in combination with each
other or with other keys to increase the number of
ways and the speed with which you can move the
cursor. Read the software documentation; the
faster and more efficiently you are able to move
the cursor through a document or database, the
faster and more efficiently you will get the job
done. Some keyboards have separate arrow keys
for cursor control. This is particularly helpful
when you are doing a lot of data entry of
numbers.
SCROLL LOCK KEY Applications software
uses the SCROLL LOCK mode of the key to
control screen scrolling.
PAUSE KEY The PAUSE key is used to
interrupt program execution.
PRT SCreen KEY The PRT SCREEN key is
activated by depressing it in conjunction with the
SHIFT key depressed. This sends whatever is
displayed on the monitor’s screen to the printer.
INSert and DELete KEYS These keys allow
you to insert or delete a character at the position
of the cursor when neither the SHIFT nor the
NUM LOCK keys are depressed.
It is important to remember that any key or
combination of keys can be assigned special meaning
by a program. Therefore, the keys may have different
meanings and functions, depending on the program you
are using. Once again, we remind you, read all the
documentation that comes with each program and with
the computer system.
Disks and Disk Drives
Magnetic disks, regardless of their type or size, are,
without a doubt, the most important secondary storage
medium used with microcomputers. Disks provide fast
retrieval of information.
The disk’s physical
characteristics, flat and round, allow the disk drive
direct access to data. Put simply, the processing unit
goes directly to a designated disk drive, seeks out the
specific location on the disk where the data is stored,
and immediately retrieves it. The disk drive does NOT
have to read through a series of records before reaching
the one desired, as is the case with magnetic tape units.
The two forms of magnetic disk typically used with
microcomputers are the floppy disk (diskette) and the
hard disk. Let’s look at the sizes and construction of
each and at the disk drive devices that read from and
write to them.
DISKETTES AND THEIR DRIVES.— A
diskette is also referred to as a floppy disk, or just plain
floppy, because it is a round, flexible platter.
Physical Characteristics.— The platter is
enclosed in a plastic jacket. At present, diskettes come
in two sizes (diameters): 5 1/4 (5.25) inches and 3 1/2
1-18
