OS
OS
Application
software
User
Reference
Software
Virtual memory
Application software
(Runs on system software platform)
“Virtual memory” is a function that uses
a portion of auxiliary storage devices
such as hard disks to execute large
programs that exceed the main storage
capacity. When executing multiple programs at the same time, or editing large
data such as an image file, memory can
be insufficient. In such a case, some of
the data in the main memory is temporarily saved to a hard disk or other device, effectively providing more memory
than the physical capacity of the main
memory.
Reference
Profile
A “profile” is a collection of information
for each user account that is unique to
each environment. It manages settings
such as the desktop layout, network
configuration, and human interface configuration.
Reference
User account
A “user account,” also referred to as an
“account,” is a collection of information
such as a user name or password that
is required to utilize a computer. A user
account is linked to a single profile, and
when the user logs on to the user account, the computer reads the information in the profile.
Reference
Multitask
“Multitask” refers to the CPU function in
which multiple tasks are executed at the
same time. Multitasking enables multiple programs including word processing
software and spreadsheet software to
run at the same time, and allows alternation between the two programs.
In contrast, a CPU that can only execute one task at a time is considered to
be “single-tasking.”
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System software
Middleware
Basic software
(Acts as interface between hardware and application
software, and humans)
Hardware
2
OS functions
The functions of an OS are summarized below.
Function
Description
Memory management
Manages the memory domain for efficient memory use.
Virtual memory enables more memory to be used than
physically available.
Resource
management
Allocates and manages computer resources (CPU, memory, hard disk, software) for efficient use of resources.
Input/output
management
(Device management)
Manages and controls peripherals such as a keyboard or
printer. Recent OSes are “plug and play” to enable the
easy use of peripherals.
File management
Enables reading and writing of files in devices such as hard
disks and floppy disks. Restrictions on file and folder usage
within the computer can be placed for each user.
User management
Enables registration and deletion of multiple user accounts
on a computer. Information such as access rights and profiles are managed for each registered user account.
Task management
Manages the programs that are currently in operation. The
execution unit of a program is called a “task.” Recent OSes
possess the capability to multitask, and are able to perform
multiple tasks at the same time.