CSE 80 -- Glossary of Terms
- device file
- An entry in the filesystem name space
referring to a hardware device. In most Unix filesystems, the
convention is that device files are all in the /dev
directory, though Solaris uses /devices and /dev
both. By making hardware devices appear as files, many standard
utility programs may be used with hardware devices without special
modification by I/O redirection or by using the device file names as
- dollar expansion
- Dollar expansion refers to the shell's
expansion of shell and environment variables. Strings of alphanumeric
characters preceeded by $ are interpreted as names of shell
or environment variables, and the shell replaces that string (and the
dollar sign) with the value of the variable.
- Globbing refers to the expansion of shell
metacharacters to complete file names. Shell globbing metacharacters
are '*' and '?', which expands to a sequence of zero or more
characters and exactly one character respectively.
- Mounting refers to the attachment of a filesystem
subtree (that is completely resident on a disk drive) to the currently
accessible filesystem tree. The mount point, a directory in the
currently accessible filesystem (typically an empty directory) becomes
synonymous with the root directory of the subtree from the new drive,
and the original contents of the mount point becomes invisible and
inaccessible until the filesystem is dismounted.
- mount point
- See mount.
- operating system
- The operating system is the combination of
the operating system kernel (or just `kernel' for short) and various
system programs. These system programs are critical for the operation
of the system but run above the kernel; examples of these are the
programs (/etc/rc or /etc/init.d) that bring the system up for
multi-user use, ones for system maintennence such as backing up the
filesystem data (dump/restore), etc.
- operating system kernel
- The lowest level software responsible
for managing the hardware. It is responsible for allocation of
resources such as CPU time, available memory (in Unix and most other
operating systems, as virtual memory), disk space (as a filesystem).
Another purpose of the kernel is protection. Multiuser operating
systems like Unix provide the user-id abstraction, so that programs
run under one user-id can not erase or alter the files of another user
without explicit permission, and one buggy program can not cause
another independent program to crash.
- (process ID) The process ID is a number that uniquely
identifies a process.
- A process is a running program.
- process image
- The memory contents of a process. The initial
process image is described by the executable file, which contains the
contents of the read-only text (instruction) portions and the contents
of the mutable initialized data areas. Uninitialized data just has
its location and size described so that the operating system can zero
fill this when a process is created, saving space in the executable
- system call
- A system call is a request to the operating
system kernel. These are accomplished using special instructions that
forces a context switch to the kernel, which then figures out what the
process wanted it to do.
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