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 Unix operating 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 Unix operating 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.
CLS may refer to:
In computing, CLS
(for clear screen) is a command used by the command line interpreters COMMAND.COM and CMD.EXE on DOS, OS/2 and Microsoft Windows operating systems to clear the screen or console window of commands and any output generated by them. It does not clear the user's history of commands, however. The command is also available in the DEC RT-11 operating system. In other environments, such as Linux and Unix, the same functionality is provided by the clear command.
While the ultimate origins of using the three-character string CLS as the command to clear the screen likely predate Microsoft's use, this command was present before its MS-DOS usage, in the embedded ROM BASIC dialects Microsoft wrote for early 8-bit microcomputers (such as TRS-80 Color BASIC), where it served the same purpose. The MS-DOS dialects of BASIC written by Microsoft, BASICA and GW-BASIC, also have the CLS command as a BASIC keyword - as do various non-Microsoft implementations of BASIC such as BBC BASIC found on the BBC Micro computers. The CLS command is also present in BASIC versions for Microsoft Windows, however this generally clears text printed on the form, rather than the whole screen or controls on the form.
Chime or chimes may refer to:
A carillon-like instrument with fewer than 23 bells is called a chime.
American chimes usually have one to one and a half diatonic octaves. Many chimes are automated.
The first bell chime was created in 1487. Before 1900, chime bells typically lacked dynamic variation and the inner tuning (the mathematical balance of a bell's complex sound) required to permit the use of harmony. Since then, chime bells produced in Belgium, the Netherlands, England, and America have inner tuning and can produce fully harmonized music. Some towers in England hung for full circle change ringing chime by an Ellacombe apparatus.
The Macintosh startup sequence behaviors include the startup chime, Happy Mac, Sad Mac and Chimes of Death.
The Macintosh startup chime is the single note or chord (depending on model type) played when an Apple Macintosh computer is turned on. The sound indicates that diagnostic tests run immediately at startup have found no hardware or fundamental software problems.
Mark Lentczner created the code for the arpeggiated chord used on the Macintosh II. Variations of this sound were used until Jim Reekes created the startup chime used for the Quadra 700 through the Quadra 800. Reekes said, "The startup sound was done in my home studio on a Korg Wavestation. It's a C major chord, played with both hands stretched out as wide as possible (with 3rd at the top, if I recall)." He was also the creator of the iconic (or "earconic", as he calls it) "bong" startup chime used in most Macintoshes since the Quadra 840AV. A slightly lower-pitched version of this chime was used on all PCI-based Power Macs until the iMac G3. The Macintosh LC, LC II, and Macintosh Classic II do not use the Reekes chime, instead using an F major chord that just produces a "ding" sound. The first generation of Power Macintosh computers also do not use the Reekes chime, instead using a chord strummed on a Yamaha 12-string acoustic guitar by jazz guitarist Stanley Jordan. Further, the Power Macintosh 5200–6300 computers (excluding the 5400 and 5500, which still had the "bong" chime) used an exclusive chime not used on any other Macintosh model, and the 20th Anniversary Macintosh also used a special startup chime as well, exclusive to this particular Macintosh.