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82-462: Forth typically combines a compiler with an integrated command shell, where the user interacts via subroutines called words . Words can be defined, tested, redefined, and debugged without recompiling or restarting the whole program. All syntactic elements, including variables, operators, and control flow, are defined as words. A stack is used to pass parameters between words, leading to a Reverse Polish notation style. For much of Forth's existence,

164-413: A call stack , a special case of the stack data structure , to implement function calls and returns. Each procedure call creates a new entry, called a stack frame , at the top of the stack; when the procedure returns, its stack frame is deleted from the stack, and its space may be used for other procedure calls. Each stack frame contains the private data of the corresponding call, which typically includes

246-444: A compiler or assembler . He changed direction with colorForth , which uses internal tokens in the source code to guide a tiny compiler. He chose to visualize these tokens as different colors in a program, so code to be compiled and code to be interpreted are displayed distinctly. In the 2000s he created a series of low-power chips, marketed by GreenArrays, containing up to 144 individual stack processors. Moore began programming at

328-435: A peripheral device , accessing a file , halting the program or the machine, or temporarily pausing program execution. Side effects are considered undesireble by Robert C. Martin , who is known for promoting design principles. Martin argues that side effects can result in temporal coupling or order dependencies. Charles H. Moore Charles Havice Moore II (born 9 September 1938), better known as Chuck Moore ,

410-473: A Forth compiler are the words that fetch and store a byte, and the word that commands a Forth word to be executed. Often the most time-consuming part of writing a remote port is constructing the initial program to implement fetch, store and execute, but many modern microprocessors have integrated debugging features (such as the Motorola CPU32 ) that eliminate this task. The basic data structure of Forth

492-788: A basic Forth system has led to many personal and proprietary variants, such as the custom Forth used to implement the bestselling 1986 video game Starflight from Electronic Arts . Forth is used in the Open Firmware boot loader , in spaceflight applications such as the Philae spacecraft , and in other embedded systems which involve interaction with hardware. Moore developed a series of microprocessors for executing compiled Forth-like code directly and experimented with smaller languages based on Forth concepts, including cmForth and colorForth . Most of these languages were designed to support Moore's own projects, such as chip design. Forth has

574-485: A capability to programming that has commonality. The term used tends to reflect the context in which it is used – usually based on the language being used. For example: The idea of a callable unit was initially conceived by John Mauchly and Kathleen Antonelli during their work on ENIAC and recorded in a January 1947 Harvard symposium on "Preparation of Problems for EDVAC -type Machines." Maurice Wilkes , David Wheeler , and Stanley Gill are generally credited with

656-647: A dedicated hardware stack to store return addresses—such hardware supports only a few levels of subroutine nesting, but can support recursive subroutines. Machines before the mid-1960s—such as the UNIVAC I , the PDP-1 , and the IBM 1130 —typically use a calling convention which saved the instruction counter in the first memory location of the called subroutine. This allows arbitrarily deep levels of subroutine nesting but does not support recursive subroutines. The IBM System/360 had

738-417: A different name for a callable unit that returns a value ( function or subprogram ) vs. one that does not ( subroutine or procedure ). Other languages, such as C , C++ , C# and Lisp , use only one name for a callable unit, function . The C-family languages use the keyword void to indicate no return value. If declared to return a value, a call can be embedded in an expression in order to consume

820-415: A larger and different set of words from the stand-alone Forth's PAUSE word for task creation, suspension, destruction and modification of priority. A full-featured Forth system with all source code will compile itself, a technique commonly called meta-compilation or self-hosting , by Forth programmers (although the term doesn't exactly match meta-compilation as it is normally defined). The usual method

902-421: A library, in the literal sense, which kept indexed collections of tapes or decks of cards for collective use. To remove the need for self-modifying code , computer designers eventually provided an indirect jump instruction, whose operand, instead of being the return address itself, was the location of a variable or processor register containing the return address. On those computers, instead of modifying

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984-620: A niche in astronomical and space applications as well as a history in embedded systems . The Open Firmware boot ROMs used by Apple , IBM , Sun , and OLPC XO-1 contain a Forth environment. Forth has often been used to bring up new hardware. Forth was the first resident software on the new Intel 8086 chip in 1978, and MacFORTH was the first resident development system for the Macintosh 128K in 1984. Atari, Inc. used an elaborate animated demo written in Forth to showcase capabilities of

1066-443: A powerful programming tool. The primary purpose is to allow for the decomposition of a large and/or complicated problem into chunks that have relatively low cognitive load and to assign the chunks meaningful names (unless they are anonymous). Judicious application can reduce the cost of developing and maintaining software, while increasing its quality and reliability. Callable units are present at multiple levels of abstraction in

1148-419: A reverse Polish syntax in which the parameters of an instruction precede the instruction. A typical reverse Polish assembler prepares the operands on the stack and the mnemonic copies the whole instruction into memory as the last step. A Forth assembler is by nature a macro assembler, so that it is easy to define an alias for registers according to their role in the Forth system: e.g. "dsp" for the register used as

1230-468: A scratch area. Swapping tasks is simple and efficient; as a result, Forth multitaskers are available even on very simple microcontrollers , such as the Intel 8051 , Atmel AVR , and TI MSP430 . Other non-standard facilities include a mechanism for issuing calls to the host OS or windowing systems , and many provide extensions that employ the scheduling provided by the operating system. Typically they have

1312-456: A sequence of numbers, and so on through the list of subroutines needed for a particular problem. ... All these subroutines will then be stored in the machine, and all one needs to do is make a brief reference to them by number, as they are indicated in the coding. Kay McNulty had worked closely with John Mauchly on the ENIAC team and developed an idea for subroutines for the ENIAC computer she

1394-432: A serial line. Classic Forth systems traditionally use neither operating system nor file system . Instead of storing code in files, source code is stored in disk blocks written to physical disk addresses. The word BLOCK is employed to translate the number of a 1K-sized block of disk space into the address of a buffer containing the data, which is managed automatically by the Forth system. Block use has become rare since

1476-484: A spreadsheet program competing with Lotus 1-2-3 , were written in Forth. The Canon Cat (1987) uses Forth for its system programming. Rockwell produced single-chip microcomputers with resident Forth kernels: the R65F11 and R65F12. ASYST was a Forth expansion for measuring and controlling on PCs. The Forth programming language was used in the production of Star Wars: Episode IV – A New Hope . Specifically, it

1558-427: A subroutine call instruction that placed the saved instruction counter value into a general-purpose register; this can be used to support arbitrarily deep subroutine nesting and recursive subroutines. The Burroughs B5000 (1961) is one of the first computers to store subroutine return data on a stack. The DEC PDP-6 (1964) is one of the first accumulator-based machines to have a subroutine call instruction that saved

1640-462: A subroutine called MYSUB from the main program. The subroutine would be coded as The JSB instruction placed the address of the NEXT instruction (namely, BB) into the location specified as its operand (namely, MYSUB), and then branched to the NEXT location after that (namely, AA = MYSUB + 1). The subroutine could then return to the main program by executing the indirect jump JMP MYSUB, I which branched to

1722-499: Is a version of Forth with graphics extensions for the Apple II. Common practice was codified in the de facto standards FORTH-79 and FORTH-83 in the years 1979 and 1983, respectively. These standards were unified by ANSI in 1994, commonly referred to as ANS Forth. As of 2018, the source for the original 1130 version of FORTH has been recovered, and is now being updated to run on a restored or emulated 1130 system. Forth emphasizes

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1804-454: Is an American computer engineer and programmer, best known for inventing the Forth programming language in 1968. He cofounded FORTH, Inc., with Elizabeth Rather in 1971 and continued to evolve the language with an emphasis on simplicity. Beginning in the early 1980s, Moore shifted focus to designing stack machines in hardware conjoined with Forth-like languages to run on them. He developed

1886-406: Is defined by a simple algorithm. The interpreter reads a line of input from the user input device, which is then parsed for a word using spaces as a delimiter ; some systems recognise additional whitespace characters. When the interpreter finds a word, it looks the word up in the dictionary . If the word is found, the interpreter executes the code associated with the word, and then returns to parse

1968-415: Is most obvious and objectionable in leaf procedures or leaf functions , which return without making any procedure calls themselves. To reduce that overhead, many modern compilers try to delay the use of a call stack until it is really needed. For example, the call of a procedure P may store the return address and parameters of the called procedure in certain processor registers, and transfer control to

2050-418: Is possible, since all the logical characteristics essential to this procedure are available, to evolve a coding instruction for placing the subroutines in the memory at places known to the machine, and in such a way that they may easily be called into use. In other words, one can designate subroutine A as division and subroutine B as complex multiplication and subroutine C as the evaluation of a standard error of

2132-419: Is the "dictionary" which maps "words" to executable code or named data structures. The dictionary is laid out in memory as a tree of linked lists with the links proceeding from the latest (most recently) defined word to the oldest, until a sentinel value , usually a NULL pointer, is found. A context switch causes a list search to start at a different leaf. A linked list search continues as the branch merges into

2214-425: Is to redefine the handful of words that place compiled bits into memory. The compiler's words use specially named versions of fetch and store that can be redirected to a buffer area in memory. The buffer area simulates or accesses a memory area beginning at a different address than the code buffer. Such compilers define words to access both the target computer's memory, and the host (compiling) computer's memory. After

2296-401: Is used to declare no return value; for example void in C, C++ and C#. In some languages, such as Python, the difference is whether the body contains a return statement with a value, and a particular callable may return with or without a value based on control flow. In many contexts, a callable may have side effect behavior such as modifying passed or global data, reading from or writing to

2378-438: Is usually implemented as a contiguous area of memory. It is an arbitrary design choice whether the bottom of the stack is the lowest or highest address within this area, so that the stack may grow forwards or backwards in memory; however, many architectures chose the latter. Some designs, notably some Forth implementations, used two separate stacks, one mainly for control information (like return addresses and loop counters) and

2460-583: The Atari 8-bit computers in department stores. Electronic Arts published multiple video games in the 1980s that were written in Forth, including Worms? (1983), Adventure Construction Set (1984), Amnesia (1986), Starflight (1986), and Lords of Conquest (1986). Robot coding game ChipWits (1984) was written in MacFORTH. Ashton-Tate's RapidFile (1986), a flat-file database program, and VP-Planner from Paperback Software International (1983),

2542-466: The C programming language using the conditional operator '?:' This function is written more succinctly as: This can be run as follows: First a number (1 or 8) is pushed onto the stack, FLOOR5 is called, which pops the number again and pushes the result. CR moves the output to a new line (again, this is only here for readability). Finally, a call to . pops the result and prints. Forth's grammar has no official specification. Instead, it

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2624-442: The code field (CF) and the parameter field (PF). Head and body of a dictionary entry are treated separately because they may not be contiguous. For example, when a Forth program is recompiled for a new platform, the head may remain on the compiling computer, while the body goes to the new platform. In some environments (such as embedded systems ) the heads occupy memory unnecessarily. However, some cross-compilers may put heads in

2706-524: The execution of a program. Execution continues at the next instruction after the call instruction when it returns control. The features of implementations of callable units evolved over time and varies by context. This section describes features of the various common implementations. Most modern programming languages provide features to define and call functions, including syntax for accessing such features, including: Some languages, such as Pascal , Fortran , Ada and many dialects of BASIC , use

2788-497: The IBM System/360 , for example, the branch instructions BAL or BALR, designed for procedure calling, would save the return address in a processor register specified in the instruction, by convention register 14. To return, the subroutine had only to execute an indirect branch instruction (BR) through that register. If the subroutine needed that register for some other purpose (such as calling another subroutine), it would save

2870-524: The Novix NC4000 and ShBoom (which evolved into the Ignite processor), then the minimal instruction set MuP21, and i21. He distanced himself from Forth proper, which by then had an official standard, and built ever more minimalist stack languages to support his own needs, particularly processor design . In the early 1990s, he implemented a system called OK for direct editing of x86 machine code without

2952-590: The Sh-Boom processor. Starting in 1990, he developed his own VLSI CAD system, OKAD, to overcome limitations in existing CAD software. He used these tools to develop several multi-core minimal instruction set computer (MISC) chips: the MuP21 in 1990 and the F21 in 1993. Moore was a founder of iTv Corp, one of the first companies to work on internet appliances . In 1996 he designed another custom chip for this system,

3034-708: The Smithsonian Astrophysical Observatory by the late 1950s. He attended the Massachusetts Institute of Technology and received a bachelors in physics in 1961. He entered Stanford University for graduate school to study mathematics but in 1965 he left to move to New York City to become a freelance programmer. In 1968, while employed at the United States National Radio Astronomy Observatory (NRAO), Moore invented

3116-401: The United States National Radio Astronomy Observatory (NRAO). After their work at NRAO, Charles Moore and Elizabeth Rather formed FORTH, Inc. in 1973, refining and porting Forth systems to dozens of other platforms in the next decade. Moore saw Forth as a successor to compile-link-go third-generation programming languages , or software for "fourth generation" hardware. He recalls how the name

3198-450: The application. Forth has been called a meta-application language : a language that can be used to create problem-oriented languages . Forth relies on implicit use of a data stack and reverse Polish notation which is commonly used in calculators from Hewlett-Packard . In RPN, the operator is placed after its operands, as opposed to the more common infix notation where the operator is placed between its operands. Postfix notation makes

3280-423: The beginning of a new definition, in this case a new word (again, word is the term used for a subroutine) called FLOOR5 . The text in parentheses is a comment, advising that this word expects a number on the stack and will return a possibly changed number (on the stack). The subroutine uses the following commands: DUP duplicates the number on the stack; 6 pushes a 6 on top of the stack; < compares

3362-546: The call stack mechanism can be viewed as the earliest and simplest method for automatic memory management . However, another advantage of the call stack method is that it allows recursive function calls , since each nested call to the same procedure gets a separate instance of its private data. In a multi-threaded environment, there is generally more than one stack. An environment that fully supports coroutines or lazy evaluation may use data structures other than stacks to store their activation records. One disadvantage of

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3444-448: The call stack mechanism is the increased cost of a procedure call and its matching return. The extra cost includes incrementing and decrementing the stack pointer (and, in some architectures, checking for stack overflow ), and accessing the local variables and parameters by frame-relative addresses, instead of absolute addresses. The cost may be realized in increased execution time, or increased processor complexity, or both. This overhead

3526-439: The callable declares as formal parameters . A caller passes actual parameters , a.k.a. arguments , to match. Different programming languages provide different conventions for passing arguments. In some languages, such as BASIC, a callable has different syntax (i.e. keyword) for a callable that returns a value vs. one that does not. In other languages, the syntax is the same regardless. In some of these languages an extra keyword

3608-492: The data stack pointer. Most Forth systems run under a host operating system such as Microsoft Windows , Linux or a version of Unix and use the host operating system's file system for source and data files; the ANSI Forth Standard describes the words used for I/O. All modern Forth systems use normal text files for source, even if they are embedded. An embedded system with a resident compiler gets its source via

3690-470: The early 1980s, to discover the recalculation dependencies in a spreadsheet. Namely, a location was reserved in each cell to store the return address. Since circular references are not allowed for natural recalculation order, this allows a tree walk without reserving space for a stack in memory, which was very limited on small computers such as the IBM PC . Most modern implementations of a function call use

3772-426: The fetch and store operations are redefined for the code space, the compiler, assembler, etc. are recompiled using the new definitions of fetch and store. This effectively reuses all the code of the compiler and interpreter. Then, the Forth system's code is compiled, but this version is stored in the buffer. The buffer in memory is written to disk, and ways are provided to load it temporarily into memory for testing. When

3854-579: The formal invention of this concept, which they termed a closed sub-routine , contrasted with an open subroutine or macro . However, Alan Turing had discussed subroutines in a paper of 1945 on design proposals for the NPL ACE , going so far as to invent the concept of a return address stack . The idea of a subroutine was worked out after computing machines had already existed for some time. The arithmetic and conditional jump instructions were planned ahead of time and have changed relatively little, but

3936-422: The function's return jump, the calling program would store the return address in a variable so that when the function completed, it would execute an indirect jump that would direct execution to the location given by the predefined variable. Another advance was the jump to subroutine instruction, which combined the saving of the return address with the calling jump, thereby minimizing overhead significantly. In

4018-462: The i21. Moore developed the colorForth dialect of Forth, a language derived from the scripting language for his custom VLSI CAD system, OKAD. In 2001, he rewrote OKAD in colorForth and designed the c18 processor. In 2005, Moore co-founded and became Chief Technology Officer of IntellaSys, which develops and markets his chip designs, such as the seaForth-24 multi-core processor . In 2009, he co-founded and became CTO of GreenArrays, Inc which

4100-487: The initial version of the Forth language to help control radio telescopes . In 1971 he co-founded (with Elizabeth Rather ) FORTH, Inc., the first, and still one of the leading, purveyors of Forth solutions. During the 1970s he ported Forth to dozens of computer architectures. In the 1980s, Moore turned his attention and Forth development techniques to CPU design , developing several stack machine microprocessors and gaining several microprocessor -related patents along

4182-446: The input stream, and waits for new user input. The definition of a new word is started with the word : (colon) and ends with the word ; (semi-colon). For example, will compile the word X , and makes the name findable in the dictionary. When executed by typing 10 X at the console this will print 11 10 . Most Forth systems include an assembler to write words using the processor's facilities. Forth assemblers often use

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4264-418: The language easier to parse and extend; Forth's flexibility makes a static BNF grammar inappropriate, and it does not have a monolithic compiler. Extending the compiler only requires writing a new word, instead of modifying a grammar and changing the underlying implementation. Using RPN, one can get the result of the mathematical expression (25 * 10 + 50) this way: First the numbers 25 and 10 are put on

4346-412: The location stored at location MYSUB. Compilers for Fortran and other languages could easily make use of these instructions when available. This approach supported multiple levels of calls; however, since the return address, parameters, and return values of a subroutine were assigned fixed memory locations, it did not allow for recursive calls. Incidentally, a similar method was used by Lotus 1-2-3 , in

4428-444: The main trunk leading eventually back to the sentinel, the root. There can be several dictionaries. In rare cases such as meta-compilation a dictionary might be isolated and stand-alone. The effect resembles that of nesting namespaces and can overload keywords depending on the context. A defined word generally consists of head and body with the head consisting of the name field (NF) and the link field (LF), and body consisting of

4510-553: The mid-1990s. In a hosted system those blocks too are allocated in a normal file in any case. Multitasking , most commonly cooperative round-robin scheduling , is normally available (although multitasking words and support are not covered by the ANSI Forth Standard). The word PAUSE is used to save the current task's execution context, to locate the next task, and restore its execution context. Each task has its own stacks, private copies of some control variables and

4592-459: The new version appears to work, it is written over the previous version. Numerous variations of such compilers exist for different environments. For embedded systems , the code may instead be written to another computer, a technique known as cross compilation , over a serial port or even a single TTL bit, while keeping the word names and other non-executing parts of the dictionary in the original compiling computer. The minimum definitions for such

4674-496: The other for data. The former was, or worked like, a call stack and was only indirectly accessible to the programmer through other language constructs while the latter was more directly accessible. When stack-based procedure calls were first introduced, an important motivation was to save precious memory. With this scheme, the compiler does not have to reserve separate space in memory for the private data (parameters, return address, and local variables) of each procedure. At any moment,

4756-522: The procedure's body by a simple jump. If the procedure P returns without making any other call, the call stack is not used at all. If P needs to call another procedure Q , it will then use the call stack to save the contents of any registers (such as the return address) that will be needed after Q returns. In general, a callable unit is a list of instructions that, starting at the first instruction, executes sequentially except as directed via its internal logic. It can be invoked (called) many times during

4838-408: The procedure's parameters and internal variables, and the return address. The call sequence can be implemented by a sequence of ordinary instructions (an approach still used in reduced instruction set computing (RISC) and very long instruction word (VLIW) architectures), but many traditional machines designed since the late 1960s have included special instructions for that purpose. The call stack

4920-421: The program instructions into memory from a punched paper tape . Each subroutine could then be provided by a separate piece of tape, loaded or spliced before or after the main program (or "mainline" ); and the same subroutine tape could then be used by many different programs. A similar approach was used in computers that loaded program instructions from punched cards . The name subroutine library originally meant

5002-492: The programming environment. For example, a programmer may write a function in source code that is compiled to machine code that implements similar semantics . There is a callable unit in the source code and an associated one in the machine code, but they are different kinds of callable units – with different implications and features. The meaning of each callable term (function, procedure, method, ...) is, in fact, different. They are not synonymous . Nevertheless, they each add

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5084-555: The register's contents to a private memory location or a register stack . In systems such as the HP 2100 , the JSB instruction would perform a similar task, except that the return address was stored in the memory location that was the target of the branch. Execution of the procedure would actually begin at the next memory location. In the HP 2100 assembly language, one would write, for example to call

5166-408: The rest of the input stream. If the word isn't found, the word is assumed to be a number and an attempt is made to convert it into a number and push it on the stack; if successful, the interpreter continues parsing the input stream. Otherwise, if both the lookup and the number conversion fail, the interpreter prints the word followed by an error message indicating that the word is not recognised, flushes

5248-415: The return address in a stack addressed by an accumulator or index register. The later PDP-10 (1966), PDP-11 (1970) and VAX-11 (1976) lines followed suit; this feature also supports both arbitrarily deep subroutine nesting and recursive subroutines. In the very early assemblers, subroutine support was limited. Subroutines were not explicitly separated from each other or from the main program, and indeed

5330-516: The return value. For example, a square root callable unit might be called like y = sqrt(x) . A callable unit that does not return a value is called as a stand-alone statement like print("hello") . This syntax can also be used for a callable unit that returns a value, but the return value will be ignored. Some older languages require a keyword for calls that do not consume a return value, like CALL print("hello") . Most implementations, especially in modern languages, support parameters which

5412-420: The source code of a subroutine could be interspersed with that of other subprograms. Some assemblers would offer predefined macros to generate the call and return sequences. By the 1960s, assemblers usually had much more sophisticated support for both inline and separately assembled subroutines that could be linked together. One of the first programming languages to support user-written subroutines and functions

5494-634: The special instructions used for procedure calls have changed greatly over the years. The earliest computers and microprocessors, such as the Manchester Baby and the RCA 1802 , did not have a single subroutine call instruction. Subroutines could be implemented, but they required programmers to use the call sequence—a series of instructions—at each call site . Subroutines were implemented in Konrad Zuse 's Z4 in 1945. In 1945, Alan M. Turing used

5576-457: The stack contains only the private data of the calls that are currently active (namely, which have been called but haven't returned yet). Because of the ways in which programs were usually assembled from libraries, it was (and still is) not uncommon to find programs that include thousands of functions, of which only a handful are active at any given moment. For such programs, the call stack mechanism could save significant amounts of memory. Indeed,

5658-488: The stack. The word * takes the top two numbers from the stack, multiplies them, and puts the product back on the stack. Then the number 50 is placed on the stack. The word + adds the top two values, pushing the sum. CR ( carriage return ) starts the output on a new line. Finally, . prints the result. As everything has completed successfully, the Forth system prints OK . Even Forth's structural features are stack-based. For example: The colon indicates

5740-465: The standard technique was to compile to threaded code , which can be interpreted faster than bytecode . One of the early benefits of Forth was size: an entire development environment—including compiler, editor, and user programs—could fit in memory on an 8-bit or similarly limited system. No longer constrained by space, there are modern implementations that generate optimized machine code like other language compilers. The relative simplicity of creating

5822-452: The target if the target itself is expected to support an interactive Forth. The exact format of a dictionary entry is not prescribed, and implementations vary. Subroutine In computer programming , a function (also procedure , method , subroutine , routine , or subprogram ) is a callable unit of software logic that has a well-defined interface and behavior and can be invoked multiple times. Callable units provide

5904-482: The terms "bury" and "unbury" as a means of calling and returning from subroutines. In January 1947 John Mauchly presented general notes at 'A Symposium of Large Scale Digital Calculating Machinery' under the joint sponsorship of Harvard University and the Bureau of Ordnance, United States Navy. Here he discusses serial and parallel operation suggesting ...the structure of the machine need not be complicated one bit. It

5986-496: The top two numbers on the stack (6 and the DUP ed input), and replaces them with a true-or-false value; IF takes a true-or-false value and chooses to execute commands immediately after it or to skip to the ELSE ; DROP discards the value on the stack; 5 pushes a 5 on top of the stack; and THEN ends the conditional. The FLOOR5 word is equivalent to this function written in

6068-409: The use of small, simple functions called words . Words for bigger tasks call upon many smaller words that each accomplish a distinct sub-task. A large Forth program is a hierarchy of words. These words, being distinct modules that communicate implicitly via a stack mechanism, can be prototyped, built and tested independently. The highest level of Forth code may resemble an English-language description of

6150-656: The way. His designs have all emphasized high performance at low power usage. He also explored alternate Forth architectures such as cmForth and machine Forth, which more closely matched his chips' machine languages. In 1983 Moore founded Novix, Inc., where he developed the NC4000 processor. This design was licensed to Harris Semiconductor which marketed an enhanced version as the RTX2000 , a radiation hardened stack processor which has been used in numerous NASA missions. In 1985 at his consulting firm Computer Cowboys, he developed

6232-446: Was FORTRAN II . The IBM FORTRAN II compiler was released in 1958. ALGOL 58 and other early programming languages also supported procedural programming. Even with this cumbersome approach, subroutines proved very useful. They allowed the use of the same code in many different programs. Memory was a very scarce resource on early computers, and subroutines allowed significant savings in the size of programs. Many early computers loaded

6314-466: Was called F-O-R-T-H, a five-letter abbreviation of FOURTH, standing for fourth-generation computer language. That was the day, you may remember, of third-generation computers and I was going to leapfrog. But because FORTH ran on the 1130 (which permitted only five-character identifiers), the name was shortened. FORTH, Inc.'s microFORTH was developed for the Intel 8080 , Motorola 6800 , Zilog Z80 , and RCA 1802 microprocessors, starting in 1976. MicroFORTH

6396-446: Was coined: At Mohasco ["in the late 1960s"] I also worked directly on an IBM 1130 interfaced with an IBM 2250 graphics display. The 1130 was a very important computer: it had the first cartridge disk, as well as a card reader, a card punch (as backup for the disk), and a console typewriter. The 1130 let the programmer, for the first time, totally control the computer interactively. FORTH first appeared as an entity on that 1130. It

6478-432: Was crucial for combining live-action footage with model shots and other visual effects. Forth was chosen for its efficiency and its ability to handle real-time processing required for these intricate tasks. Forth evolved from Charles H. Moore 's personal programming system, which had been in continuous development since 1968. Forth was first exposed to other programmers in the early 1970s, starting with Elizabeth Rather at

6560-531: Was later used by hobbyists to generate Forth systems for other architectures, such as the 6502 in 1978. The Forth Interest Group was formed in 1978. It promoted and distributed its own version of the language, FIG-Forth, for most makes of home computer. Forth was popular in the early 1980s, because it was well suited to the limited memory of microcomputers . The ease of implementing the language led to many implementations. The Jupiter ACE home computer has Forth in its ROM -resident operating system. Insoft GraFORTH

6642-478: Was programming during World War II. She and the other ENIAC programmers used the subroutines to help calculate missile trajectories. Goldstine and von Neumann wrote a paper dated 16 August 1948 discussing the use of subroutines. Some very early computers and microprocessors, such as the IBM 1620 , the Intel 4004 and Intel 8008 , and the PIC microcontrollers , have a single-instruction subroutine call that uses

6724-566: Was used to control the Dystraflex motion control system, which was created by John Dykstra and his team at Industrial Light & Magic . This system was instrumental in creating the complex and precise camera movements required for the space battle scenes and the trench run sequences on the Death Star . The Dystraflex system allowed for the pre-programming of camera movements, which could then be repeated exactly for multiple takes. This

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