Glossary 111
Hard drive
Also called
fixed
disk. A hard drive is connected to the computer and can be
installed or removed. Data written to a hard drive remains until it is overwritten
or corrupted.
The 2.5-inch hard drive in your computer was designed for use in a notebook
computer. Because hard drives in notebook computers are smaller than those in
desktop computers, their maximum storage capacity may be less than that of
desktop hard drives. However, because of their smaller size, the drives handle
shock and vibration better than larger drives, which is important for a notebook
computer.
I/O
Input/output. Refers to peripheral devices, such as printers, that are addressed
through an I/O address.
I/O address
I/O stands for input/output. Peripheral devices, such as printers, are addressed
through the I/O port address.
IRQ (interrupt request line)
The IRQ is a hardware line that a device uses to signal the microprocessor when
the device needs the microprocessor’s services. The number of IRQs is limited by
industry standards.
LCD (liquid-crystal display)
The LCD screen on your computer differs from the display screen of a desktop
monitor. Most desktop monitors use CRT (cathode-ray tube) displays, which
work by moving an electron beam across phosphor dots on the back of the screen.
The phosphor dots light up to show the image. LCDs use a liquid-crystal solution
between two sheets of polarizing material. Electric current passing through the
liquid aligns the crystals so that light can or cannot pass through them, creating an
image.
MB (megabyte)
1,024 kilobytes.
Megabit
1,048,576 bits or about 128 kilobytes.
Operating system
A program that supervises the computer's operation, including handling I/O.
Application programs and users can request operating-system services. A user
might request operation-system services to copy files or format a disk. An
application program might use the operating system to obtain keyboard input,
write data to a file, or write data to a screen.
