The uninitiated data segment of a running program.
It is allocated when the program starts running
and is not present in the executable program on disk.
An image of a terminated process
saved for debugging.
A core file is created under the name core
in the current directory of the process
when an abnormal event occurs
that results in the process's termination.
A refinement of paging in which
it is not necessary to load in
the entire contents of the text and data segments
of a program from disk when the process is started.
Instead, pages are brought into memory as they are accessed.
Demand paging is enabled by
hardware features of the 80386 and 80486 processors
that are supported by the operating system.
A peripheral piece of equipment used for I/O operations.
The UNIX system uses the philosophy
of separating processes from I/O devices
to allow flexibility.
Device files, also called ``special device files''
or ``device nodes,''
are located under the /dev directory
and are used to access the device driver
from user-level programs.
A piece of program code linked into the kernel
to handle all read, write, and control operations
on a particular device.
A number, usually associated with a group name,
used by the system to identify the group owner
of files and directories.
The GID of a process
becomes the group owner of files
created by the process and descendant processes.
A GID identifies a group of UIDs.
The control structure for all files
on UNIX operating systems.
Inode stands for Index Node,
and is the focus of all file activities
in the UNIX filesystem.
Each file has one inode
that defines the file's type
(regular, directory, device, and so forth),
the location on disk, the size of the file,
access permissions, access times, and so forth.
Note that the file's name is not stored in the inode;
instead, the directory associates filenames with inodes.
The basic memory-resident software on which the UNIX system relies.
It is responsible for most operating system functions,
including scheduling and managing processes
and filesystem maintenance.
To make a filesystem available for use
by attaching it to a point in the hierarchical filesystem.
This is done with either the
command or the
The capability of a computer or operating system
to appear to run more than one task at a time.
A mechanism by which a process can occupy
less physical memory than is allocated
in the logical address space.
Performed through the division of memory
into pages that can be paged in from or out to
the swap area on disk.
Describes an operating system
where the task-switching operation
can occur at any point.
The kernel can preempt the operation of any process
in order to switch tasks.
The process need not relinquish control
or signify in any way that it is ready to be switched.
Relative ordering given to a process
with respect to other processes.
System processes have a higher priority
than user processes.
An instance of a program
that is at some stage of execution.
In UNIX operating systems,
it also refers to the execution of a computer environment,
including contents of memory, register values,
name of the current working directory,
status of files,
information recorded at login time,
and so forth.
A new process is initiated
when a user types the name of a file
that represents an executable program
or when another user-level process
executes such a file.
A mode of operation in the 80386 and 80486
in which it is possible to make use of
the processor's architectural features
for multitasking operating systems.
A portion of virtual memory associated
with an executing process.
Each executing process has a region for its
text segment, its data segment, and its stack segment,
and may have an additional region for
a shared memory segment.
Permissions that allow you to read or write
any file or internal data structure on the system.
``Superuser'' is the word used to describe
someone working with root permissions,
but these two terms are often used interchangably
to refer to UID 0.
An area of hard disk set aside for use by
the memory management subsystem.
A request by an active process
for a service performed by the UNIX system kernel,
such as I/O or process creation.
All system operations are allocated,
initiated, monitored, manipulated, and terminated
through system calls.
System calls allow a user-level program
to do work that the program
would not normally be able to do.
The segment that contains
binary machine language instructions,
equivalent to program code.
The real time during which a process
is actually running on the processor.
usually associated with a login name,
used by the system to identify owners of files and directories.
The UID of a process
becomes the owner of files created by the process
and descendant processes.
Logically-assigned memory that
may or may not exist physically.
Through the use of paging and the swap area,
more memory can be referenced and allocated
than actually exists on the system.