Environment variables are a set of dynamic named values that can affect the way running processes will behave on a computer.
They are part of the environment in which a process runs. For example, a running process can query the value of the TEMP environment variable to discover a suitable location to store temporary files, or the HOME or USERPROFILE variable to find the directory structure owned by the user running the process.
They were introduced in their modern form in 1979 with Version 7 Unix, so are included in all Unixoperating system flavors and variants from that point onward including Linux and OS X. From PC DOS 2.0 in 1982, all succeeding Microsoft operating systems including Microsoft Windows, and OS/2 also have included them as a feature, although with somewhat different syntax, usage and standard variable names.
In all Unix and Unix-like systems, each process has its own separate set of environment variables. By default, when a process is created, it inherits a duplicate environment of its parent process, except for explicit changes made by the parent when it creates the child. At the API level, these changes must be done between running fork and exec. Alternatively, from command shells such as bash, a user can change environment variables for a particular command invocation by indirectly invoking it via env or using the ENVIRONMENT_VARIABLE=VALUE <command> notation. All Unixoperating system flavors, DOS, and Windows have environment variables; however, they do not all use the same variable names. A running program can access the values of environment variables for configuration purposes.
A television channel is a physical or virtual channel over which a television station or television network is distributed. For example, in North America, "channel 2" refers to the broadcast or cable band of 54 to 60 MHz, with carrier frequencies of 55.25MHz for NTSC analog video (VSB) and 59.75MHz for analog audio (FM), or 55.31MHz for digital ATSC (8VSB). Channels may be shared by many different television stations or cable-distributed channels depending on the location and service provider.
A coast guard or coastguard is a maritime security organization of a particular country. The term implies widely different responsibilities in different countries, from being a heavily armed military force with customs and security duties to being a volunteer organization tasked with search and rescue functions and lacking any law enforcement powers. However, a typical coast guard's functions are distinct from typical functions of both the navy (a pure military force) and a transportation police (a civilian law enforcement agency).
Each Water Guard station was issued with Manby's Mortar which was invented by Captain George William Manby in 1808. The mortar fired a shot with a line attached from the shore to the wrecked ship and was used for many years up and down the coastline. This began the process in which the Coastguard assumed a life saving role. In 1821 a committee of inquiry recommended that responsibility for the Preventative Water Guard be transferred to the Board of Customs. The Treasury agreed and in a Minute dated 15 January 1822, directed that the preventative services, which consisted of the Preventative Water Guard, cruisers, and Riding Officers should be placed under the authority of the Board of Customs and in future should be named the Coast Guard. In 1845 the Coastguard was subordinated to the Admiralty.