D686: Operating Systems for Computer Scientists

file

The smallest logical storage unit; a collection of related information defined by its creator.

text file

A type of file containing text (alphanumeric characters).

source file

A file containing the source code of a program

executable file

A file containing a program that is ready to be loaded into memory and executed.

extended file attributes

Extended metadata about a file, including items such as character encoding details, file checksums, etc

file info window

A GUI view of the file metadata

write pointer

The location in a file to which the next write will occur

read pointer

The location in a file from which the next read will occur.

current-file-position pointer

A per-process pointer to the location in a file to which the next read or from which the next write will occur.

seek

The operation of changing the current file-position pointer.

hard links

File-system links in which a file has two or more names pointing to the same inode.

open-file table

An operating system data structure containing details of every file open within the system

open count

The number of processes having an open file

shared lock

A file lock similar to a reader lock in that several processes can obtain the lock concurrently

exclusive lock

A file lock similar to a writer lock in that only one process at a time can obtain the lock.

advisory file-lock mechanism

A file-locking system in which the operating system does not enforce locking and file access, leaving it to processes to implement the details.

shell script

A file containing a set series of commands (similar to a batch file) that are specific to the shell being used.

magic number

A crude method of storing a number at the start of a file to indicate the type of the data in the file

sequential access

A file-access method in which contents are read in order, from beginning to end

direct access

A file-access method in which contents are read in random order, or at least not sequentially

relative access

A file-access method in which contents are read in random order, or at least not sequentially.

logical records

File contents logically designated as fixed-length structured data

relative block number

An index relative to the beginning of a file. The first relative block of the file is block 0, the next is block 1, and so on through the end of the file.

allocation problem

The determination by the operating system of where to store the blocks of a file.

index

In file systems, an access method built on top of direct access in which a file contains an index with pointers to the contents of the file.

user file directory (UFD)

In two-level directory implementation, a per-user directory of files

main file directory (MFD)

In two-level directory implementation, the index pointing to each UFD.

path name

The file-system name for a file, which contains all the mount-point and directory-entry information needed to locate the file (e.g., "C:/foo/bar.txt" and "/foo/bar.txt")

search path

In some operating systems, the sequence of directories searched for an executable file when a command is executed.

absolute path name

A path name starting at the top of the file system hierarchy.

relative path name

A path name starting at a relative location (such as the current directory).

acyclic graph

In directory structure implementation, a structure that contains no cycles (loops).

link

In file naming, a file that has no contents but rather points to another file.

resolve

Generally, to translate from a symbolic representation to a numeric one. In networking, to translate from a host name to a host-id. With files, to follow a link and find the target file.

hard links

File-system links in which a file has two or more names pointing to the same inode.

garbage collection

In general, recovery of space containing no-longer-valid data.

access-control list

A list of user names allowed to access a file.

Linux commands

commands used in the Linux operating system to interact with the system, manage files, manage processes, and perform various tasks through the command-line interface 

memory mapping

A file-access method in which a file is mapped into the process memory space so that standard memory access instructions read and write the contents of the file; an alternative to the use of read() and write() calls.

file mapping

In Windows, the first step in memory-mapping a file.

view

In Windows, an address range mapped in shared memory. Also, the second step in memory-mapping a file, allowing a process to access the file contents.

named shared-memory object

In Windows API, a section of a memory-mapped file accessible by name from multiple processes.

device driver

software that allows the operating system to communicate and control different hardware devices