Information Technology Reference
In-Depth Information
Special-purpose computers. This system is typical of a number of computers with
specialized functions, such as those that control sophisticated military aircraft, the space
shuttle, and some home appliances.
Figure 4.2
The Role of Operating Systems
The role of the operating system is
to act as an interface or buffer
between application software and
hardware.
Application
software
Operating
system
Hardware
The OS, which plays a central role in the functioning of the complete computer system,
is usually stored on disk. After you start, or “boot up,” a computer system, portions of the
OS are transferred to memory as they are needed. You can also boot a computer from a CD,
DVD, or even a thumb drive that plugs into a USB port. A storage device that contains some
or all of the OS is often called a “rescue disk” because you can use it to start the computer if
you have problems with the primary hard disk.
Some OSs for handheld computers and notebooks that use solid-state hard drives have
an “Instant On” feature that significantly reduces the time needed to boot a computer. The
set of programs that make up the OS performs a variety of activities, including the following:
Performing common computer hardware functions
Providing a user interface and input/output management
Providing a degree of hardware independence
Managing system memory
Managing processing tasks
Providing networking capability
Controlling access to system resources
Managing files
The kernel , as its name suggests, is the heart of the OS and controls the most critical processes.
The kernel ties all of the OS components together and regulates other programs.
kernel
The heart of the operating system,
which controls the most critical
processes.
Common Hardware Functions
All applications must perform certain hardware-related tasks, such as the following:
Get input from the keyboard or another input device
Retrieve data from disks
Store data on disks
Display information on a monitor or printer
Each of these tasks requires a detailed set of instructions. The OS converts a basic request
into the instructions that the hardware requires. In effect, the OS acts as an intermediary
between the application and the hardware. The typical OS performs hundreds of such tasks,
translating each task into one or more instructions for the hardware. The OS notifies the
user if input or output devices need attention, if an error has occurred, and if anything
abnormal happens in the system.
User Interface and Input/Output Management
One of the most important functions of any OS is providing a user interface . A user interface
allows people to access and command the computer system. The first user interfaces for
mainframe and personal computer systems were command based. A command-based user
interface requires you to give text commands to the computer to perform basic activities (see
Figure 4.3). For example, the command ERASE 00TAXRTN would cause the computer to
erase a file called 00TAXRTN. RENAME and COPY are other examples of commands used
to rename files and copy files from one location to another. Many operating systems that use
a graphical user interface, discussed next, also have powerful command-based features.
user interface
The element of the operating system
that allows you to access and com-
mand the computer system.
command-based user
interface
A user interface that requires you to
give text commands to the computer
to perform basic activities.
 
 
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