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119-406: Sinclair BASIC is a dialect of the programming language BASIC used in the 8-bit home computers from Sinclair Research , Timex Sinclair and Amstrad . The Sinclair BASIC interpreter was written by Nine Tiles Networks Ltd. Designed to run in only 1 KB of RAM , the system makes a number of decisions to lower memory usage. This led to one of Sinclair BASIC's most notable features, that
238-414: A formal language . Languages usually provide features such as a type system , variables , and mechanisms for error handling . An implementation of a programming language is required in order to execute programs, namely an interpreter or a compiler . An interpreter directly executes the source code, while a compiler produces an executable program. Computer architecture has strongly influenced
357-406: A heap and automatic garbage collection . For the next decades, Lisp dominated artificial intelligence applications. In 1978, another functional language, ML , introduced inferred types and polymorphic parameters . After ALGOL (ALGOrithmic Language) was released in 1958 and 1960, it became the standard in computing literature for describing algorithms . Although its commercial success
476-400: A logic called a type system . Other forms of static analyses like data flow analysis may also be part of static semantics. Programming languages such as Java and C# have definite assignment analysis , a form of data flow analysis, as part of their respective static semantics. Once data has been specified, the machine must be instructed to perform operations on the data. For example,
595-507: A colour-graphics board was designed, none was ever produced commercially. 1 KB RAM with the option of a 16 KB RAM-Pack, and later a 32 KB one. A PCB was also marketed by Boldfield Computing that converted the edge connector to electrical compatibility with a Sinclair ZX81, allowing use of the ZX81 16K RAM pack. All chars in Charset (based on ASCII-1967 ) being redefinable. References to
714-447: A data type whose elements, in many languages, must consist of a single type of fixed length. Other languages define arrays as references to data stored elsewhere and support elements of varying types. Depending on the programming language, sequences of multiple characters, called strings , may be supported as arrays of characters or their own primitive type . Strings may be of fixed or variable length, which enables greater flexibility at
833-415: A few extra words were added based on common BASIC sound, video and tape commands. The implementation lacked some less frequently used Forth words, these being easily implemented if needed. Runtime error checking could be turned off to raise speed by 25% to 50%. Its Forth was adapted to the disk-less tape-using home computer hardware by being able to save/load user "compiled vocabularies", instead of
952-641: A forthcoming colour video card, but no official product that used this connector was ever released. The Jupiter Ace was based on the Zilog Z80, which the designers had previous experience of from working on the Sinclair ZX81 and ZX Spectrum. Both graphics and text could be displayed at the same time: (1) redefinition of the character tiles provided standard 256×192 graphics limited to the 128 available (definable) 8×8 chars, concurrent with plotting of 64×48 graphics. Internal speaker directly controlled by
1071-422: A meaning to a grammatically correct sentence or the sentence may be false: The following C language fragment is syntactically correct, but performs operations that are not semantically defined (the operation *p >> 4 has no meaning for a value having a complex type and p->im is not defined because the value of p is the null pointer ): If the type declaration on the first line were omitted,
1190-539: A more traditional editor where the user typed-in the keyword as individual characters, similar to other home computers of the era. This required a new tokenizer to convert the line into a similar internal format. The resulting in-memory storage of the program was otherwise similar to Microsoft BASIC , in that only the keywords are presented as tokens, while non-keywords – like string and numeric constants and variable names – are left in their original typed-in format. However, that typed-in format
1309-489: A price of £ 89.95. Sales to the general public were slow. Initially the computer was only available by mail order, and Jupiter Cantab reported that there were production difficulties, but these had been overcome by January 1983 and that units were arriving in shops. The use of Forth rather than the more usual choice of BASIC, and the availability and success of the ZX Spectrum, as well as limited published software,
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#17327722017501428-445: A separate heap . The first byte for a variable entry always held the type in the first three bits, and the first character of the name in the next five bits. As was the case in most microcomputer dialects, A , A$ , A() and A$ () were all different variables and could store different values. Most variables could only have a single-character name; the exception are numeric variables (not arrays), where an alternate format held
1547-507: A serious limit on its popularity. He wanted a new kit that would expand on their previous MK14 and feature a built-in BASIC at the target price of £79.95. To meet this price point, the machine would ship with only 1 KB of RAM and 4 KB of ROM. Grant suggested using the Forth language instead, but the budget precluded this. Grant wrote the BASIC interpreter between June and July 1979, but
1666-462: A single character in memory, which was a significant savings in the early machines that shipped with only 1 KB of RAM. This single-character representation included multi-character items like <> . This has the added advantages of simplifying the runtime, as it can immediately determine whether a character in the source code is a keyword or text, and also means that keywords are never entered directly, meaning that one can, for instance, have
1785-674: A success. Jupiter Cantab was formed by Richard Altwasser and Steven Vickers . Both had been on the design team for the ZX Spectrum : Altwasser worked on ZX81 development and hardware design of the Spectrum. Vickers adapted and expanded the 4K ZX80 ROM to the 8K ZX81 ROM and wrote most of the ROM for the Spectrum. The Jupiter Ace was named after an early British computer, the Pilot ACE , and went on sale on 22 September 1982 with
1904-516: A suite of trig functions, which were expected of any BASIC from that era, producing 8K BASIC . The initial version did not support the ZX Printer and had a bug in its square root function. Nine Tiles provided a new version to address these, but Sinclair was slow to include the new version in the ROMs. The new ROMs were eventually offered to owners of the earlier ZX80 as well. When Sinclair lost
2023-433: A variable named "PRINT", as the system can determine that it is not the same as the keyword. As the systems evolved and added new keywords, the entry system became increasingly difficult to use. 48 BASIC in the Spectrum required every key to host up to four keywords. Entering keywords was a time-consuming process of looking over the relatively small type on the keyboard for the appropriate key, and then correctly entering
2142-538: A version for TC 2048 and a version for T/S 2068 and TC 2068 . Timex Extended Basic by Timex of Portugal is used on the Timex Computer 3256 , adding TEC – Timex Extended Commands commands supporting the AY-3-8912 sound chip, RS-232 network and the 512x192 pixel high resolution graphic mode. Several ZX Spectrum interpreters exist. Several ZX Spectrum compilers exist. In all colour-related commands,
2261-608: A wide variety of uses. Many aspects of programming language design involve tradeoffs—for example, exception handling simplifies error handling, but at a performance cost. Programming language theory is the subfield of computer science that studies the design, implementation, analysis, characterization, and classification of programming languages. Programming languages differ from natural languages in that natural languages are used for interaction between people, while programming languages are designed to allow humans to communicate instructions to machines. The term computer language
2380-406: Is a set of allowable values and operations that can be performed on these values. Each programming language's type system defines which data types exist, the type of an expression , and how type equivalence and type compatibility function in the language. According to type theory , a language is fully typed if the specification of every operation defines types of data to which the operation
2499-413: Is allowed to define a variable named PRINT and output its value with PRINT PRINT . This is also related to the syntax requirement that every line start with a command keyword, and pressing the one keypress for that command at the start of a line changes the editor from command mode to letter mode. Thus, variable assignment requires LET (i.e., LET a = 1 not only a = 1 ). This practice
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#17327722017502618-415: Is allowed, the fewer type errors can be detected. Early programming languages often supported only built-in, numeric types such as the integer (signed and unsigned) and floating point (to support operations on real numbers that are not integers). Most programming languages support multiple sizes of floats (often called float and double ) and integers depending on the size and precision required by
2737-542: Is also different from other BASIC dialects. Further, it meant that unlike other BASIC dialects, the interpreter needed no parentheses to identify functions; SIN x was sufficient, no SIN(x) needed (though the latter was allowed). The 4K BASIC ROM of the ZX80 had a short list of exceptions to this: the functions CHR$ () , STR$ () , TL$ () , PEEK() , CODE() , RND() , USR() and ABS() did not have one-byte tokens but were typed in letter-by-letter and required
2856-458: Is anchored around its line editor . When the machine is booted, it runs BASIC and displays an inverse video "K" at the bottom of the screen to indicate the entry point. When a line is entered and the NEW LINE key is pressed, it either runs immediately if it does not have a line number prefix, or clears the screen and performs the equivalent of a LIST command, placing a ">" cursor after
2975-419: Is applicable. In contrast, an untyped language, such as most assembly languages , allows any operation to be performed on any data, generally sequences of bits of various lengths. In practice, while few languages are fully typed, most offer a degree of typing. Because different types (such as integers and floats ) represent values differently, unexpected results will occur if one type is used when another
3094-469: Is expected. Type checking will flag this error, usually at compile time (runtime type checking is more costly). With strong typing , type errors can always be detected unless variables are explicitly cast to a different type. Weak typing occurs when languages allow implicit casting—for example, to enable operations between variables of different types without the programmer making an explicit type conversion. The more cases in which this type coercion
3213-403: Is often used to specify the execution semantics of languages commonly used in practice. A significant amount of academic research goes into formal semantics of programming languages , which allows execution semantics to be specified in a formal manner. Results from this field of research have seen limited application to programming language design and implementation outside academia. A data type
3332-484: Is performance; the math library included tests to look for the zero exponent, and if it was seen, it would not attempt to perform various operations on the remaining 3 bytes under certain conditions. The ZX81 8K BASIC used the shorter forms GOTO , GOSUB , CONT and RAND , whereas the Spectrum 48 BASIC used the longer forms GO TO , GO SUB , CONTINUE and RANDOMIZE . The ZX80 4K BASIC also used these longer forms but differed by using
3451-444: Is simply building a new Forth Word). In short, "Interpreting mode" means Run stage, while "Compiling mode" refers to an Editing stage. Avoiding sources was compensated by storing comments entered in the code with the compiled output, traditional compilation would discard such comments. The comments were then recovered on decompiling. As a result of "code is the source", modified words (edited) would demand actualization of all code using
3570-444: Is sometimes used interchangeably with "programming language". However, usage of these terms varies among authors. In one usage, programming languages are described as a subset of computer languages. Similarly, the term "computer language" may be used in contrast to the term "programming language" to describe languages used in computing but not considered programming languages – for example, markup languages . Some authors restrict
3689-474: Is stored. The simplest user-defined type is an ordinal type whose values can be mapped onto the set of positive integers. Since the mid-1980s, most programming languages also support abstract data types , in which the representation of the data and operations are hidden from the user , who can only access an interface . The benefits of data abstraction can include increased reliability, reduced complexity, less potential for name collision , and allowing
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3808-460: Is the most prominent example of such a character code. Related computers running Sinclair BASIC used similar variants, e.g. the ZX80 or ZX81 character sets . All of these different but related character sets included Sinclair BASIC tokens. One uncommon feature of Sinclair BASIC is the way it stores variables in memory. Typically, interpreters use a fixed-size entry to hold data, making it easy to scan
3927-442: Is the potential for errors to go undetected. Complete type inference has traditionally been associated with functional languages such as Haskell and ML . With dynamic typing, the type is not attached to the variable but only the value encoded in it. A single variable can be reused for a value of a different type. Although this provides more flexibility to the programmer, it is at the cost of lower reliability and less ability for
4046-402: Is used (in languages that require such declarations) or that the labels on the arms of a case statement are distinct. Many important restrictions of this type, like checking that identifiers are used in the appropriate context (e.g. not adding an integer to a function name), or that subroutine calls have the appropriate number and type of arguments, can be enforced by defining them as rules in
4165-481: Is usually defined using a combination of regular expressions (for lexical structure) and Backus–Naur form (for grammatical structure). Below is a simple grammar, based on Lisp : This grammar specifies the following: The following are examples of well-formed token sequences in this grammar: 12345 , () and (a b c232 (1)) . Not all syntactically correct programs are semantically correct. Many syntactically correct programs are nonetheless ill-formed, per
4284-658: The CREATE .. DOES> , creation pair with: These two defining pairs, instead of one alone, allowed the Ace to decompile its programs, unlike usual Forth systems. This decompiling ability was a solution to the absence of the more flexible disk system used by Forth. Not storing the source of a Forth program, but compiling the code after editing, it avoided completely the emulation of a disk/tape drive on RAM saving computer memory . It also saved time in reading and writing programs from cassette tape. This tape-friendly and RAM-saving solution
4403-723: The CPU in single task mode, with control of sound frequency and duration in milliseconds . Storage was through a cassette-tape interface at 1500 baud . Files could be used for either storage of Forth programs (compiled code) or raw dumps of memory. The Ace had an 8 KB ROM containing the Forth kernel and operating system, and the predefined dictionary of Forth words in about 5 KB. The remaining 3 KB of ROM supported several functionalities: floating-point numbers library and character definitions table, tape recorder access, decompiling and redefining newly re-edited 'words' (i.e. routines). Some of
4522-509: The CPU that performs instructions on data is separate, and data must be piped back and forth to the CPU. The central elements in these languages are variables, assignment , and iteration , which is more efficient than recursion on these machines. Many programming languages have been designed from scratch, altered to meet new needs, and combined with other languages. Many have eventually fallen into disuse. The birth of programming languages in
4641-473: The Commodore 64 or Atari 8-bit computers , the up and down keys can be used to move among the lines in the program and edit them in-place. The most notable feature of the editor is that keywords are entered using single keystrokes. For instance, on the ZX81, the P key on the keyboard would cause the entire keyword PRINT to be entered into the currently editing line. Once a keyword has been entered,
4760-576: The Jupiter Ace project. When the Spectrum was launched the ROM was still not complete, and although Nine Tiles continued working on it until April 1982, by that point 75,000 Spectrums had already been sold and the project was cancelled. The missing functionality was later added by additional code in the ZX Interface 1 . After Nine Tiles and Sinclair went their own ways, several new versions of 48 BASIC were created. In 1983, as part of introducing
4879-561: The ROM was written in Z80 machine code , but some was also coded in Forth. The next 8 KB was built in RAM that was only partially decoded , with 2 KB of video RAM echoed twice, and 1 KB of user RAM echoed 4 times (with the same memory appearing at several different memory addresses). Using the lower-address mirror of the video RAM would select CPU priority, resulting in some momentary random pixels on
Sinclair BASIC - Misplaced Pages Continue
4998-441: The shift key – the systems did not initially support lowercase text, so the shift was not otherwise needed. The keywords below the keys required a second keystroke, ⇧ Shift + NEW LINE , which put the editor into "function mode", changing the cursor to an "F". Entering common code often resulted in a significant number of keystrokes. The system has the advantage of representing all multi-character keywords as
5117-455: The 1950s was stimulated by the desire to make a universal programming language suitable for all machines and uses, avoiding the need to write code for different computers. By the early 1960s, the idea of a universal language was rejected due to the differing requirements of the variety of purposes for which code was written. Desirable qualities of programming languages include readability, writability, and reliability. These features can reduce
5236-592: The Ace RAM sometimes include the separate 2 KB video memory, which was not available for programming, thus leading to some confusion. Similarly, it is sometimes argued that because of Forth's efficiency, the 1 KB standard RAM was in effect comparable to at least 2 KB on a BASIC system. Its most distinctive characteristic was the choice of Forth, a structured language. Threaded compilation allowed programs written to run nearly as fast as many native- compiled languages loaded by more expensive computers. Forth
5355-425: The Ace's monochrome. This restricted sales largely to a niche market of technical programming enthusiasts. The Jupiter Ace is often compared with ZX81 due to its similar size, low cost, and similar form factor . Internally its design is more similar to the ZX Spectrum although the Ace also had a dedicated video memory of 2 KB, partly avoiding the slow down when programs accessed the same bank (same chips) as
5474-465: The Jupiter Ace will depend on the machine-buying public's acceptance of another microcomputer language." Further, there was only a very limited range of published software – either commercial programs or type-in programs printed in hobby magazines – for the machine, and these were restricted by the base model's small amount of RAM. Attempts to promote the Ace in
5593-572: The Spectrum to the US market as the TS2068, Timex modified it as T/S 2000 BASIC . The new version was incapable of running many Spectrum programs due to the memory location of machine's functions moving. A similar, but somewhat more compatible version, was introduced as part of the Spanish Spectrum 128 of 1985, 128 BASIC . Amstrad purchased Sinclair Research in 1986. As Sinclair had never owned
5712-572: The ZX81 only), ** (replaced with ↑ on the Spectrum). These are expanded by referencing a token table in ROM. Thus, a keyword uses one byte of memory only, a significant saving over traditional letter-by-letter storage. This also meant that the BASIC interpreter could quickly determine any command or function by evaluating one byte, and that the keywords need not be reserved words like in other BASIC dialects or other programming languages, e.g., it
5831-542: The code initially came in at 5 KB and he spent the next month trimming it down. It was initially an incomplete implementation of the 1978 American National Standards Institute (ANSI) Minimal BASIC standard with integer arithmetic only, termed 4K BASIC . Even before the ZX80 was introduced in February 1980, the constant downward price-pressure in the industry was allowing the already inexpensive design to be further reduced in complexity and cost. In particular, many of
5950-487: The code is reached; this is called finalization. There is a tradeoff between increased ability to handle exceptions and reduced performance. For example, even though array index errors are common C does not check them for performance reasons. Although programmers can write code to catch user-defined exceptions, this can clutter a program. Standard libraries in some languages, such as C, use their return values to indicate an exception. Some languages and their compilers have
6069-515: The contest to build the BBC Computer , he moved ahead with plans to produce a low-cost colour-capable machine that emerged as the ZX Spectrum of April 1982. ROM space would once again be increased, this time to 16 KB. In keeping with his philosophy of making systems for the lowest possible expenditure, Sinclair wanted the absolute minimum changes to the existing 8K BASIC. Although Nine Tiles felt that something much better would be needed for
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#17327722017506188-448: The copyright to the language, Amstrad had to arrange a new license with Nine Tiles. Several other versions also appeared in this period as various extensions and clones of the Spectrum were introduced. These included +3 BASIC , BASIC64 and Timex Extended Basic . As of 2015, interpreters exist for modern operating systems , and older systems, that allow Sinclair Basic to be used easily. Like most home-computer BASICs, Sinclair BASIC
6307-402: The cost of increased storage space and more complexity. Other data types that may be supported include lists , associative (unordered) arrays accessed via keys, records in which data is mapped to names in an ordered structure, and tuples —similar to records but without names for data fields. Pointers store memory addresses, typically referencing locations on the heap where other data
6426-408: The cost of readability. Natural-language programming has been proposed as a way to eliminate the need for a specialized language for programming. However, this goal remains distant and its benefits are open to debate. Edsger W. Dijkstra took the position that the use of a formal language is essential to prevent the introduction of meaningless constructs. Alan Perlis was similarly dismissive of
6545-432: The cost of training programmers in a language, the amount of time needed to write and maintain programs in the language, the cost of compiling the code, and increase runtime performance. Programming language design often involves tradeoffs. For example, features to improve reliability typically come at the cost of performance. Increased expressivity due to a large number of operators makes writing code easier but comes at
6664-442: The cursor changes to an "L" to indicate what follows will be interpreted as normal text. For instance, pressing P again at this point would enter a single letter "P". Keys generally had two separate keywords assigned to them – one above it and one below. Pressing the key in "K" mode would enter the keyword above the key, like PRINT for P . If the system was in "L" mode, one could return to "K" by pressing
6783-516: The design of programming languages, with the most common type ( imperative languages —which implement operations in a specified order) developed to perform well on the popular von Neumann architecture . While early programming languages were closely tied to the hardware , over time they have developed more abstraction to hide implementation details for greater simplicity. Thousands of programming languages—often classified as imperative, functional , logic , or object-oriented —have been developed for
6902-433: The details of the hardware, instead being designed to express algorithms that could be understood more easily by humans. For example, arithmetic expressions could now be written in symbolic notation and later translated into machine code that the hardware could execute. In 1957, Fortran (FORmula TRANslation) was invented. Often considered the first compiled high-level programming language, Fortran has remained in use into
7021-471: The educational market also failed; doubts over whether Forth would be relevant for exam syllabuses, and the lack of support for Forth from teaching staff were key issues. Pupils were more interested in learning the widely used BASIC than a language used by only one (uncommon) machine with a peculiar RPN syntax. Finally, the tile -based graphics compared poorly to the pixel -based graphics of other machines – which were also colour rather than
7140-447: The entry for "B$ ", it fails to match A with B, then reads the type to see it is a string, and then has to read the following length byte and skip forward by that amount of bytes to find the next entry in the table. To make this somewhat easier, arrays also stored a two-byte length, so the entire structure could be skipped over more easily. A unique feature was the "short float", or integer type. Any numeric variable could store either type,
7259-416: The first character of the name in those same five bits, but was then followed by additional characters ending with one with its high-bit set. Long variable names were whitespace-independent, and case-insensitive in later versions, so LET Number Of Apples = 5 is the same as LET numberofapples = 5 referred to the same variable. The downside to this approach is that scanning the table to look up
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#17327722017507378-461: The first programming languages. The earliest computers were programmed in first-generation programming languages (1GLs), machine language (simple instructions that could be directly executed by the processor). This code was very difficult to debug and was not portable between different computer systems. In order to improve the ease of programming, assembly languages (or second-generation programming languages —2GLs) were invented, diverging from
7497-532: The following Sinclair QL , as well as a number of 3rd-party BASICs for the Spectrum and its various clones. The original version continued to be modified and ported in the post-Sinclair era. Clive Sinclair initially met with John Grant, the owner of Nine Tiles, in April 1979 to discuss a BASIC for Sinclair's new computer concept. Sinclair was inspired to make a new machine after watching his son enjoy their TRS-80 , but that machine's £500 price tag appeared to be
7616-404: The following six new keywords: BASIC64 by Timex of Portugal , is a software extension to allow better Basic programming with the 512×192 and dual display areas graphic modes available only on Timex Sinclair computers. This extension adds commands and does a complete memory remap to avoid the system overwriting the extended screen memory area. Two versions exist due to different memory maps –
7735-399: The idea. Jupiter Ace The Jupiter Ace by Jupiter Cantab was a British home computer released in 1982. The Ace differed from other microcomputers of the time in that its programming environment used Forth instead of the more popular BASIC . This difference, along with limited available software and poor character based graphic display, limited sales and the machine was not
7854-532: The introduction of the ZX Spectrum 128 at which time the 16 KB Spectrum was no longer sold and most existing ones in use had been upgraded to 48 KB. 128 BASIC is the BASIC for the ZX Spectrum 128. It offers extra commands and uses letter-by-letter input. +3 BASIC is the BASIC with disk support for the ZX Spectrum +3 and +2A. T/S 2000 BASIC is used on the Spectrum-compatible Timex Sinclair 2068 (T/S 2068) and adds
7973-402: The invention of the microprocessor , computers in the 1970s became dramatically cheaper. New computers also allowed more user interaction, which was supported by newer programming languages. Lisp , implemented in 1958, was the first functional programming language. Unlike Fortran, it supported recursion and conditional expressions , and it also introduced dynamic memory management on
8092-464: The keywords were entered using single keystrokes; each of the possible keywords was mapped to a key on the keyboard, when pressed, the token would be placed into memory while the entire keyword was printed out on-screen. This made code entry easier whilst simplifying the parser . The original ZX80 version supported only integer mathematics, which partially made up for some of the memory-saving design notes which had negative impact on performance. When
8211-429: The language's rules; and may (depending on the language specification and the soundness of the implementation) result in an error on translation or execution. In some cases, such programs may exhibit undefined behavior . Even when a program is well-defined within a language, it may still have a meaning that is not intended by the person who wrote it. Using natural language as an example, it may not be possible to assign
8330-417: The languages intended for execution. He also argues that textual and even graphical input formats that affect the behavior of a computer are programming languages, despite the fact they are commonly not Turing-complete, and remarks that ignorance of programming language concepts is the reason for many flaws in input formats. The first programmable computers were invented at the end of the 1940s, and with them,
8449-563: The left or right array position respectively; for example a$ ( TO 5) is equivalent to LEFT$ (a$ ,5) . Further, a$ (5) alone is enough to replace MID$ (a$ ,5,1) . On the 16K/48K ZX Spectrum ( 48 BASIC) , there are 88 keywords in Sinclair BASIC, denoting commands (of which there are 50), functions and logical operators (31), and other keywords (16, including 9 which are also commands or functions): 4K BASIC for ZX80 (so named for residing in 4 KiB read-only memory (ROM)),
8568-439: The line number in the most recently entered line. In contrast to most machines of the era, the editor does not allow freeform editing at any point on the screen. Instead, when the user presses EDIT , the current line of code is copied back to the bottom of the screen. The user can move horizontally through this line using the cursor keys and commits their changes by pressing NEW LINE again. In contrast, on machines like
8687-511: The machine language to make programs easier to understand for humans, although they did not increase portability. Initially, hardware resources were scarce and expensive, while human resources were cheaper. Therefore, cumbersome languages that were time-consuming to use, but were closer to the hardware for higher efficiency were favored. The introduction of high-level programming languages ( third-generation programming languages —3GLs)—revolutionized programming. These languages abstracted away
8806-400: The meaning of languages, as opposed to their form ( syntax ). Static semantics defines restrictions on the structure of valid texts that are hard or impossible to express in standard syntactic formalisms. For compiled languages, static semantics essentially include those semantic rules that can be checked at compile time. Examples include checking that every identifier is declared before it
8925-441: The memory map was used for ROM, Video and User-available RAM, leaving the second 16 KB of the memory map free for RAM extension and the topmost 32 KB undefined. One 1K bank allowed redefinition of most of its 128 ASCII -based characters in 8×8 pixel bitmap format. The other 1K bank stored the full screen display of 24 rows × 32 columns of characters in black and white. Colour was intended to be achieved as expansion, but although
9044-522: The multiple keystrokes needed to enter it properly. For instance, entering BEEP required one to type CAPS SHIFT + SYMBOL SHIFT to access extended mode (later models include a separate EXTENDED MODE key), keeping SYMBOL SHIFT held down, and then and pressing Z . To improve the complex entry on the Spectrum, the keywords were colour-coded to indicate the required mode: This concept had run its course, and later machines running 128 BASIC (ZX Spectrum 128, +2, +3, +2A, and +2B) featured
9163-405: The new machine, the schedule would not allow it, and yet another expansion of the original code was produced. Due to the RAM also being increased, to 48 KB, this version was known as 48K BASIC and eventually 48 BASIC with the introduction of the ZX Spectrum 128 at which time the 16 KB Spectrum was no longer sold and most existing ones in use had been upgraded to 48 KB. The new version
9282-639: The new programming languages uses static typing while a few numbers of new languages use dynamic typing like Ring and Julia . Some of the new programming languages are classified as visual programming languages like Scratch , LabVIEW and PWCT . Also, some of these languages mix between textual and visual programming usage like Ballerina . Also, this trend lead to developing projects that help in developing new VPLs like Blockly by Google . Many game engines like Unreal and Unity added support for visual scripting too. Every programming language includes fundamental elements for describing data and
9401-480: The number 8 may be used to indicate “transparent” while in INK and PAPER may also be set to 9 for “contrast” — that is, to put a dark colour on a light background or vice versa automatically. Dialect (computing) A programming language is a system of notation for writing computer programs . Programming languages are described in terms of their syntax (form) and semantics (meaning), usually defined by
9520-423: The one newly edited. This was done with the non standard REDEFINE command. Although not explicitly designed for such a purpose, the compiled Forth could be utilised for ROM extensions to the built in system. External ROMs were developed with Ace Forth to be used as control applications. The machine was able to use some ZX81 add-ons due to similar RAM locations, and external expansion slot. Jupiter Cantab made
9639-455: The operations or transformations applied to them, such as adding two numbers or selecting an item from a collection. These elements are governed by syntactic and semantic rules that define their structure and meaning, respectively. A programming language's surface form is known as its syntax . Most programming languages are purely textual; they use sequences of text including words, numbers, and punctuation, much like written natural languages. On
9758-436: The option of turning on and off error handling capability, either temporarily or permanently. One of the most important influences on programming language design has been computer architecture . Imperative languages , the most commonly used type, were designed to perform well on von Neumann architecture , the most common computer architecture. In von Neumann architecture, the memory stores both data and instructions, while
9877-436: The order of execution of key instructions via the use of semaphores , controlling access to shared data via monitor , or enabling message passing between threads. Many programming languages include exception handlers, a section of code triggered by runtime errors that can deal with them in two main ways: Some programming languages support dedicating a block of code to run regardless of whether an exception occurs before
9996-483: The other hand, some programming languages are graphical , using visual relationships between symbols to specify a program. The syntax of a language describes the possible combinations of symbols that form a syntactically correct program. The meaning given to a combination of symbols is handled by semantics (either formal or hard-coded in a reference implementation ). Since most languages are textual, this article discusses textual syntax. The programming language syntax
10115-560: The parentheses. They were listed as the INTEGRAL FUNCTIONS on a label above and to the right of the keyboard. 128 BASIC , present on ZX Spectrum 128, +2, +3, +2A, and +2B, stored keywords internally in one-byte code points, but used a conventional letter-by-letter BASIC input system. It also introduced two new commands: The original Spanish ZX Spectrum 128 included four additional BASIC editor commands in Spanish, one of which
10234-442: The parsing phase. Languages that have constructs that allow the programmer to alter the behavior of the parser make syntax analysis an undecidable problem , and generally blur the distinction between parsing and execution. In contrast to Lisp's macro system and Perl's BEGIN blocks, which may contain general computations, C macros are merely string replacements and do not require code execution. The term semantics refers to
10353-399: The poor case and small initial memory all weighed against wider market acceptance. Eventually Jupiter Cantab ceased trading by the end of October 1983. The brand was then acquired by Boldfield Computing Ltd in 1984 that sold the remaining stock by mail order for £26. The brand was again sold to Paul Andrews's company Andrews UK Limited in 2015. Sales of the machine were never very large;
10472-585: The program would trigger an error on the undefined variable p during compilation. However, the program would still be syntactically correct since type declarations provide only semantic information. The grammar needed to specify a programming language can be classified by its position in the Chomsky hierarchy . The syntax of most programming languages can be specified using a Type-2 grammar, i.e., they are context-free grammars . Some languages, including Perl and Lisp, contain constructs that allow execution during
10591-489: The programmer specifies a desired result and allows the interpreter to decide how to achieve it. During the 1980s, the invention of the personal computer transformed the roles for which programming languages were used. New languages introduced in the 1980s included C++, a superset of C that can compile C programs but also supports classes and inheritance . Ada and other new languages introduced support for concurrency . The Japanese government invested heavily into
10710-417: The programmer. Storing an integer in a type that is too small to represent it leads to integer overflow . The most common way of representing negative numbers with signed types is twos complement , although ones complement is also used. Other common types include Boolean —which is either true or false—and character —traditionally one byte , sufficient to represent all ASCII characters. Arrays are
10829-420: The programming language to check for errors. Some languages allow variables of a union type to which any type of value can be assigned, in an exception to their usual static typing rules. In computing, multiple instructions can be executed simultaneously. Many programming languages support instruction-level and subprogram-level concurrency. By the twenty-first century, additional processing power on computers
10948-439: The reported number of Aces sold before Jupiter Cantab closed for business was around 5,000. As of the early 2000s, surviving machines are uncommon, often fetching high prices as collector's items. Forth, while being structured and powerful, was considered difficult to learn, and a knowledge of BASIC acquired from familiarity with other home computers was of no practical help in learning it. A 1982 review stated that "The success of
11067-427: The screen when video subsystem and the CPU accessed the video RAM in the same clock cycle . Using the higher-address would briefly pause the CPU on the interference, affecting the program timing and making this mode unsuitable for I/O operations. Since video RAM was partially separated from the main address and data busses, for the most part the video subsystem and the CPU could operate in parallel . The first 16 KB of
11186-404: The semantics may define the strategy by which expressions are evaluated to values, or the manner in which control structures conditionally execute statements . The dynamic semantics (also known as execution semantics ) of a language defines how and when the various constructs of a language should produce a program behavior. There are many ways of defining execution semantics. Natural language
11305-481: The separate circuits in the ZX80 were re-implemented in a single uncommitted logic array from Ferranti , which allowed the price to be reduced to only £49.95 while increasing the size of the ROM to 8 KB. This work was assigned to Steve Vickers , who joined Nine Tiles in January 1980. Whilst Grant worked on the code interfacing with hardware, Vickers used the larger space to introduce floating-point arithmetic and
11424-686: The so-called fifth-generation languages that added support for concurrency to logic programming constructs, but these languages were outperformed by other concurrency-supporting languages. Due to the rapid growth of the Internet and the World Wide Web in the 1990s, new programming languages were introduced to support Web pages and networking . Java , based on C++ and designed for increased portability across systems and security, enjoyed large-scale success because these features are essential for many Internet applications. Another development
11543-477: The spelling RANDOMISE . The ZX81 8K BASIC was the only version to use FAST , SCROLL , SLOW and UNPLOT . The ZX80 4K BASIC had the exclusive function TL$ () ; it was equivalent to the string operator (2 TO ) in later versions. Unique code points are assigned in the ZX80 character set , ZX81 character set and ZX Spectrum character set for each keyword or multi-character operator, i.e. <= , >= , <> , "" (tokenized on
11662-413: The storage itself did not change and used 5 bytes in either case. Integers were indicated by setting the exponent byte to zero, while floating-point values were stored with an excess-128 format exponent. This meant that it could not store zero as a float and lost one possible exponent magnitude. It also did not use any less memory, as the values were still 5-byte in memory. The advantage to this format
11781-562: The system was ported to the ZX81 in 1981, a full floating point implementation was added. This version was very slow, among the slowest BASICs on the market at the time, but given the limited capabilities of the machine, this was not a serious concern. Performance became a more serious issue with the release of the ZX ;Spectrum in 1983, which ran too slowly to make full use of the machine's new features. This led to an entirely new BASIC for
11900-525: The term "programming language" to Turing complete languages. Most practical programming languages are Turing complete, and as such are equivalent in what programs they can compute. Another usage regards programming languages as theoretical constructs for programming abstract machines and computer languages as the subset thereof that runs on physical computers, which have finite hardware resources. John C. Reynolds emphasizes that formal specification languages are just as much programming languages as are
12019-401: The twenty-first century. Around 1960, the first mainframes —general purpose computers—were developed, although they could only be operated by professionals and the cost was extreme. The data and instructions were input by punch cards , meaning that no input could be added while the program was running. The languages developed at this time therefore are designed for minimal interaction. After
12138-424: The twenty-first century. C allows access to lower-level machine operations more than other contemporary languages. Its power and efficiency, generated in part with flexible pointer operations, comes at the cost of making it more difficult to write correct code. Prolog , designed in 1972, was the first logic programming language, communicating with a computer using formal logic notation. With logic programming,
12257-475: The underlying data structure to be changed without the client needing to alter its code. In static typing , all expressions have their types determined before a program executes, typically at compile-time. Most widely used, statically typed programming languages require the types of variables to be specified explicitly. In some languages, types are implicit; one form of this is when the compiler can infer types based on context. The downside of implicit typing
12376-442: The usual numbered programming blocks used by diskette systems. Decompiling avoided wasting RAM in simulating an absent Block System, used with both disk and tape drivers (these last not to be confused with tape recorders). As replacement, it included an extra data file, for raw binary data. These solutions were unique to the Jupiter Ace. To allow decompile, it distinguished usual Forth definer and compiler words creation, replacing
12495-400: The value of a variable reference is more complex. In addition to testing whether the name matches using the subset of the first byte, if the entry is not the one that is being looked for, the type has to be read from the upper three bits and then the next location of a variable in storage calculated using the type. For instance, if the program encounters the variable "A" and the table starts with
12614-484: The variable table. Due to the extremely limited memory of the ZX series, any wasted space had to be avoided, and this led to the use of a variable-length format. The data types included numbers stored in a 5-byte values, strings with a length and then the characters, and arrays of both of those types. The data was stored in the table itself, which contrasts with most BASICs of the era, where strings and array entries were stored in
12733-487: The video memory. Like the Spectrum, the Ace used black conductive rubber keys although unlike the Spectrum, the keys had a conductive pad that was squashed directly onto tracks on the PCB rather than using a membrane. As a result, the keys would often stop working reliably until they were cleaned or the conductive material was refreshed. Audio capabilities were CPU-controlled with programmable frequency and duration. Sound output
12852-476: Was service-oriented programming , designed to exploit distributed systems whose components are connected by a network. Services are similar to objects in object-oriented programming, but run on a separate process. C# and F# cross-pollinated ideas between imperative and functional programming. After 2010, several new languages— Rust , Go , Swift , Zig and Carbon —competed for the performance-critical software for which C had historically been used. Most of
12971-497: Was available near the end of 1981, but it was "depressingly slow" and "snail like". Additionally, as no prototypes were available until the end of the year, it lacked support for the new line of peripherals Sinclair was planning. In February 1982, Nine Tiles began to have disagreements with Sinclair over owed royalties for the various manuals that Nine Tiles had produced. Around the same time, Vickers and his Sinclair counterpart, Richard Altwasser, left their respective companies to start
13090-402: Was considered well-adapted to microcomputers with their small memory and relatively low-performance processors. Forth programs are memory-efficient; as they become bigger, they reuse more previously-defined code. Control structures could be nested to any level, limited only by available memory. This allowed complex programs to be implemented, even allowing recursive programming . The Ace's Forth
13209-600: Was developed by John Grant of Nine Tiles for the ZX80. It has integer-only arithmetic. 8K BASIC is the ZX81 BASIC (also available as an upgrade for the ZX80), updated with floating-point arithmetic by Steve Vickers , so named for residing in 8 KiB ROM. 48 BASIC is the BASIC for the original 16/48 KB RAM ZX Spectrum (and clones), with colour and more peripherals added by Steve Vickers and John Grant. It resides in 16 KB ROM and began to be called 48 BASIC with
13328-407: Was increasingly coming from the use of additional processors, which requires programmers to design software that makes use of multiple processors simultaneously to achieve improved performance. Interpreted languages such as Python and Ruby do not support the concurrent use of multiple processors. Other programming languages do support managing data shared between different threads by controlling
13447-550: Was limited, most popular imperative languages—including C , Pascal , Ada , C++ , Java , and C# —are directly or indirectly descended from ALGOL 60. Among its innovations adopted by later programming languages included greater portability and the first use of context-free , BNF grammar. Simula , the first language to support object-oriented programming (including subtypes , dynamic dispatch , and inheritance ), also descends from ALGOL and achieved commercial success. C, another ALGOL descendant, has sustained popularity into
13566-521: Was not ASCII , but an internal character code that contains both printable characters and the keyword tokens. Although portions of the table, the capital letters A to Z, for instance, are in the same order as in ASCII, their characters correspond to different numeric values, i.e. their code points ' offset from zero is different from ASCII's offset of 65. Other characters, like punctuation, may have been moved about even more. The ZX Spectrum character set
13685-449: Was stated to be "ten times faster than Basic" and used less than half the memory (a significant cost percentage of low end computers of the time) of an equivalent program written in interpreted BASIC. It also allowed easy implementation of machine code routines if needed. Ace's Forth was based mostly on Forth-79, with some relevant differences, in particular it added syntax checking to control structures and definer constructions and
13804-430: Was that of dynamically typed scripting languages — Python , JavaScript , PHP , and Ruby —designed to quickly produce small programs that coordinate existing applications . Due to their integration with HTML , they have also been used for building web pages hosted on servers . During the 2000s, there was a slowdown in the development of new programming languages that achieved widespread popularity. One innovation
13923-421: Was through a small built-in speaker. As was common at the time, it used a common tape recorder instead of disk/tape drives. Similarly, a television was needed as a display – but this was in black and white only, rather than the colour supported by competing models such as the Spectrum. A secondary (undocumented) edge connector on the back of the case made some video signals available, presumably for
14042-485: Was undocumented: Unlike the LEFT$ () , MID$ () and RIGHT$ () functions used in the ubiquitous Microsoft BASIC dialects for home computers, parts of strings in Sinclair BASIC are accessed by numeric range. For example, a$ (5 TO 10) gives a substring starting with the 5th and ending with the 10th character of the variable a$ . Thus, it is possible to replace the LEFT$ () and RIGHT$ () commands by simply omitting
14161-518: Was unique to the Jupiter Ace Forth. The names can be equivocal out of a Forth context, as all Words are compiled when declared. DEFINER defines a new Class (as an array) that will build (compile) an array Object. These are active on 'Interpreter'. Pairing this Interaction mode, COMPILER defines a programming structure (usually a pair or a triplet) as IF-ELSE-THEN . These 'Structured Programming' are active on 'Compile' mode (which
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