forth
[fawrth, fohrth] 
| 1. | onward or outward in place or space; forward: to come forth; go forth. |
| 2. | onward in time, in order, or in a series: from that day forth. |
| 3. | out, as from concealment or inaction; into view or consideration: The author's true point comes forth midway through the book. |
| 4. | away, as from a place or country: to journey forth. |
| 5. | Archaic. out of; forth from. |
Forth
[fawrth, fohrth] | 1. | Firth of, an arm of the North Sea, in SE Scotland: estuary of Forth River. 48 mi. (77 km) long. |
| 2. | a river in S central Scotland, flowing E into the Firth of Forth. 116 mi. (187 km) long. |
Based on the Random House Dictionary, © Random House, Inc. 2009.
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| forth (fôrth, fōrth) adv.
Out of; forth from. [Middle English, from Old English; see per1 in Indo-European roots.] |
| Forth (fôrth, fōrth) A river of south-central Scotland flowing about 187 km (116 mi) eastward to the Firth of Forth, a wide inlet of the North Sea. |
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Published by Houghton Mifflin Company. All rights reserved.
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Forth
Forth\, v.[AS. for[eth], fr. for akin to D. voort, G. fort [root]78. See Fore, For, and cf. Afford, Further, adv.]1. Forward; onward in time, place, or order; in advance from a given point; on to end; as, from that day forth; one, two, three, and so forth. Lucas was Paul's companion, at the leastway from the sixteenth of the Acts forth. --Tyndale. From this time forth, I never will speak word. --Shak. I repeated the Ave Maria; the inquisitor bad me say forth; I said I was taught no more. --Strype. 2. Out, as from a state of concealment, retirement, confinement, nondevelopment, or the like; out into notice or view; as, the plants in spring put forth leaves. When winter past, and summer scarce begun, Invites them forth to labor in the sun. --Dryden. 3. Beyond a (certain) boundary; away; abroad; out. I have no mind of feasting forth to-night. --Shak. 4. Throughly; from beginning to end. [Obs.] --Shak. And so forth, Back and forth, From forth. See under And, Back, and From. Forth of, Forth from, out of. [Obs.] --Shak. To bring forth. See under Bring.Forth
Forth\, prep. Forth from; out of. [Archaic] Some forth their cabins peep. --Donne.Forth
Forth\, n. [OE., a ford. ? 78. See Frith.] A way; a passage or ford. [Obs.] --Todd.Cite This Source
forth
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FORTH
1.
Forth programs are structured as lists of "words" - FORTH's term which encompasses language keywords, primitives and user-defined subroutines. Forth takes the idea of subroutines to an extreme - nearly everything is a subroutine. A word is any string of characters except the separator which defaults to space. Numbers are treated specially. Words are read one at a time from the input stream and either executed immediately ("interpretive execution") or compiled as part of the definition of a new word.
The sequential nature of list execution and the implicit use of the data stack (numbers appearing in the lists are pushed to the stack as they are encountered) imply postfix syntax. Although postfix notation is initially difficult, experienced users find it simple and efficient.
Words appearing in executable lists may be "primitives" (simple assembly language operations), names of previously compiled procedures or other special words. A procedure definition is introduced by ":" and ended with ";" and is compiled as it is read.
Most Forth dialects include the source language structures BEGIN-AGAIN, BEGIN-WHILE-REPEAT, BEGIN-UNTIL, DO-LOOP, and IF-ELSE-THEN, and others can be added by the user. These are "compiling structures" which may only occur in a procedure definition.
FORTH can include in-line assembly language between "CODE" and "ENDCODE" or similar constructs. Forth primitives are written entirely in assembly language, secondaries contain a mixture. In fact code in-lining is the basis of compilation in some implementations.
Once assembled, primitives are used exactly like other words. A significant difference in behaviour can arise, however, from the fact that primitives end with a jump to "NEXT", the entry point of some code called the sequencer, whereas non-primitives end with the address of the "EXIT" primitive. The EXIT code includes the scheduler in some multi-tasking systems so a process can be descheduled after executing a non-primitive, but not after a primitive.
Forth implementations differ widely. Implementation techniques include threaded code, dedicated Forth processors, macros at various levels, or interpreters written in another language such as C. Some implementations provide real-time response, user-defined data structures, multitasking, floating-point arithmetic, and/or virtual memory.
Some Forth systems support virtual memory without specific hardware support like MMUs. However, Forth virtual memory is usually only a sort of extended data space and does not usually support executable code.
FORTH does not distinguish between operating system calls and the language. Commands relating to I/O, file systems and virtual memory are part of the same language as the words for arithmetic, memory access, loops, IF statements, and the user's application.
Many Forth systems provide user-declared "vocabularies" which allow the same word to have different meanings in different contexts. Within one vocabulary, re-defining a word causes the previous definition to be hidden from the interpreter (and therefore the compiler), but not from previous definitions.
FORTH was first used to guide the telescope at NRAO, Kitt Peak. Moore considered it to be a fourth-generation language but his operating system wouldn't let him use six letters in a program name, so FOURTH became FORTH.
Versions include fig-FORTH, FORTH 79 and FORTH 83.
FAQs. ANS Forth standard, dpANS6.
FORTH Interest Group, Box 1105, San Carlos CA 94070.
See also 51forth, F68K, cforth, E-Forth, FORML, TILE Forth.
[Leo Brodie, "Starting Forth"].
[Leo Brodie, "Thinking Forth"].
[Jack Woehr, "Forth, the New Model"].
[R.G. Loeliger, "Threaded Interpretive Languages"].
2. FOundation for Research and Technology - Hellas.
(1997-04-16)
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forth
see and so forth; back and forth; bring forth; hold forth; put forth; set forth.
Copyright © 1997. Published by Houghton Mifflin.
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