20 Computer Service and Repair
SCSI drive controllers. A driver is a small software
program written specifically for a hardware
device. It allows the operating system to properly
communicate with the device. For example, a
printer requires a specific driver to be installed
on the computer before the operating system can
successfully use the printer. Without the driver,
the printer will not function properly.
The terms firmware, BIOS, and CMOS
(pronounced c-moss) are often interchanged, but
they are really distinct concepts. Firmware is a
combination of a special type of memory chip and
software programs that support communication
and compatibility. It includes the Setup utility,
which is responsible for setting and storing the
date and time and information about the computer
hardware. CMOS is where the Setup utility stores
information about the computer’s hardware, date,
and time. It is an integrated circuit. CMOS stands
for complementary metal oxide semiconductor
and is a type of low-power semiconductor chip
technology. In the electronics field, there are many
different types of devices designed from CMOS
technology. In the computer field, it is understood
that it refers to the location where the BIOS settings
or data are stored.
Originally, firmware software was
permanently etched into a ROM (read-only
memory) chip. ROM firmware was permanent and
could only be changed by replacing the ROM chip.
Today, firmware software is stored in an EEPROM
(electrically erasable programmable read-only
memory) chip. An EEPROM is reprogrammable
and is often referred to as flash ROM. Flash ROM
can be erased electrically and reprogrammed
with an updated version of a software program.
It retains its data when electrical power to the
computer is disconnected or turned off.
BIOS is a type of firmware. It is a small
software program written in machine language.
Machine language is a language that uses
hexadecimal codes to write a program. It is the
language that your computer understands. It
is many times faster than other programming
languages, but it is much more difficult to write.
BIOS is typically 64 kB (kilobytes) in size and
has limitations on the amount of RAM it can use.
Because there is no single BIOS standard, BIOS
systems are diverse. This has led to hardware
compatibility problems that require BIOS
upgrades. Even with these disadvantages, BIOS
firmware is the most prevalent firmware in use.
EFI or UEFI is a type of firmware created
to replace BIOS. EFI was introduced in the late
1990s but was not standardized until 2005. At
that time it became known as UEFI. In contrast
to BIOS, UEFI has a standard set of boot
programs and configuration data. This allows
hardware manufacturers, software companies,
and operating systems to use the firmware in a
consistent manner and achieve similar results
without compatibility problems. It makes it much
easier to develop new hardware drivers and to
support hardware devices. Soon, UEFI will be the
most common firmware used in computers and
related hardware.
Battery
The battery supplies voltage to the CMOS,
which contains the firmware setup data,
Figure 1-30. Without the battery, the computer
would lose the date, time, and all the important
information about the hardware components
when the computer power switch is turned off.
Application Software
Operating System
Drivers and Firmware
Computer Hardware
Goodheart-Willcox Publisher
Figure 1-29. The relationship of firmware to hardware,
application software, and the operating system.