BASIC (an acronym for Beginner's All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages whose design philosophy emphasises ease of use. In 1964, John G. Kemeny and Thomas E. Kurtz designed the original BASIC language at Dartmouth College in New Hampshire. They wanted to enable students in fields additional than science and mathematics to use computers. At the time, nearly all use of computers required writing custom software, which was something only scientists and mathematicians tended to learn.

Versions of BASIC became widespread on microcomputers in the mid-1970s and 1980s. Microcomputers usually shipped with BASIC, often in the machine's firmware. Having an easy-to-learn language on these early personal computers allowed small business owners, professionals, hobbyists, and consultants to develop custom software on computers they could afford. In the 2010s, BASIC remains popular in a large number of computing dialects and in new languages influenced by BASIC, such as Microsoft's Visual Basic.

History

Before the mid-1960s, the only computers were huge mainframe computers. Users submitted jobs (calculations or additional requests) on punched cards or similar media to specialist computer operators. The computer stored these, then used a batch processing system to run this queue of jobs one after another, allowing quite high levels of utilisation of these expensive machines. As the performance of computing hardware rose through the 1960s, multi-processing was developed. This allowed a mix of batch jobs to be run together, but the real revolution was the development of time-sharing. Time-sharing allowed multiple remote interactive users to share use of the computer, interacting with the computer from computer terminals with keyboards and teletype printers, and later display screens, in much the same way as desktop computers or personal computers would be used later.

Origin

The original BASIC language was released on May 1, 1964 by John Kemeny and Thomas Kurtz and implemented under their direction by a team of Dartmouth College students. The acronym BASIC comes from the name of an unpublished paper by Thomas Kurtz. BASIC was designed to allow students to write mainframe computer programmes for the Dartmouth Time-Sharing System. It was intended specifically for less technical users who didn't have or want the mathematical background previously expected. Being able to use a computer to support teaching and research was quite novel at the time.

The language was based on FORTRAN II, with a few influences from ALGOL 60 and with additions to make it suitable for timesharing. Initially, BASIC concentrated on supporting straightforward mathematical work, with matrix arithmetic support from its initial implementation as a batch language, and character string functionality being added by 1965. Wanting use of the language to become widespread, its designers made the compiler available free of charge. (In the 1960s, software became a chargeable commodity; until then, it was provided without charge as a service with the quite expensive computers, usually available only to lease.) They additionally made it available to high schools in the Hanover area, and put considerable effort into promoting the language. In the following years, as additional dialects of BASIC appeared, Kemeny and Kurtz's original BASIC dialect became known as Dartmouth BASIC.

Spread on minicomputers

Knowledge of the relatively simple BASIC became widespread for a computer language, and it was implemented by a number of manufacturers, fitting fairly popular on newer minicomputers such as the DEC PDP series, where BASIC-PLUS was an extended dialect for use on the RSTS/E time-sharing operating system. The BASIC language was available for the Data General Nova, and additionally central to the HP Time-Shared BASIC system in the late 1960s and early 1970s, where the language was implemented as an interpreter. A version was a core part of the Pick operating system from 1973 onward, where a compiler renders it into bytecode, able to be interpreted by a virtual machine.

During this period a number of simple computer games were written in BASIC, most notably Mike Mayfield's Star Trek. A number of these were collected by DEC employee David H. Ahl and published in a newsletter he compiled. He later collected a number of these into book form, 101 BASIC Computer Games, published in 1973. During the same period, Ahl was involved in the creation of a small computer for education use, an early personal computer. When management refused to support the concept, Ahl left DEC in 1974 to found the seminal computer magazine, Creative Computing. The book remained popular, and was re-published on several occasions.

Explosive growth: the home computer era

MSX BASIC version 3.0

The introduction of the first microcomputers in the mid-1970s was the start of explosive growth for BASIC. It had the advantage that it was fairly well known to the young designers and computer hobbyists who took an interest in microcomputers. Despite Dijkstra's famous judgement in 1975, "It is practically impossible to teach good programming to students that have had a prior exposure to BASIC: as potential programmers they're mentally mutilated beyond hope of regeneration", BASIC was one of the few languages that was both high-level enough to be usable by those without training and small enough to fit into the microcomputers of the day, making it the de facto standard programming language on early microcomputers.

One of the first BASICs to seem was Tiny BASIC, a simple BASIC variant designed by Dennis Allison at the urging of Bob Albrecht of the Homebrew Computer Club. He had seen BASIC on minicomputers and felt it would be the perfect match for new machines like the MITS Altair 8800. How to design and implement a stripped-down version of an interpreter for the BASIC language was covered in articles by Allison in the first three quarterly issues of the People's Computer Company newsletter published in 1975 and implementations with source code published in Dr. Dobb's Journal of Tiny BASIC Calisthenics & Orthodontia: Running Light Without Overbyte. Versions were written by Li-Chen Wang and Tom Pittman. In 1975 MITS released Altair BASIC, developed by Bill Gates and Paul Allen as the company Micro-Soft, which eventually grew into corporate giant Microsoft. The first Altair version was co-written by Gates, Allen, and Monte Davidoff.

Almost universally, home computers of the 1980s had a ROM-resident BASIC interpreter, which the machines booted directly into. When the Apple II, PET 2001, and TRS-80 were all released in 1977, all three had BASIC as their primary programming language and operating environment. Upon boot, a BASIC interpreter in immediate mode was presented, not the command line interface used on systems running CP/M or MS-DOS. Commodore Business Machines included a version of Microsoft BASIC. The Apple II and TRS-80 each had two versions of BASIC, a smaller introductory version introduced with the initial releases of the machines and a more advanced version developed as interest in the platforms increased. As new companies entered the field, additional versions were added that subtly changed the BASIC family. The Atari 8-bit family had its own Atari BASIC that was modified in order to fit on an 8 kB ROM cartridge. The BBC published BBC BASIC, developed by Acorn Computers Ltd, incorporating a large number of additional structured programming keywords and advanced floating-point operation features.

As the popularity of BASIC grew in this period, computer magazines published complete source code in BASIC for video games, utilities, and additional programs. Given BASIC's straightforward nature, it was a simple matter to type in the code from the magazine and execute the program. Different magazines were published featuring programmes for specific computers, though a few BASIC programmes were considered universal and can be used in machines running any variant of BASIC (sometimes with minor adaptations). Many books of type-in programmes were additionally available, and in particular, Ahl published versions of the original 101 BASIC games converted into the Microsoft dialect and published it from Creative Computing as BASIC Computer Games. This book, and its sequels, provided hundreds of ready-to-go programmes that can be easily converted to practically any BASIC-running platform. The book reached the stores in 1978, just as the home computer market was starting off, and it became the first million-selling computer book. Later packages, such as Learn to Program BASIC would additionally have gaming as an introductory focus. On the business-focused CP/M computers which soon became widespread in small business environments, Microsoft BASIC (MBASIC) was one of the leading applications.

IBM PC and compatibles

When IBM was designing the IBM PC they followed the paradigm of existing home computers in wanting to have a built-in BASIC. They sourced this from Microsoft - IBM Cassette BASIC - but Microsoft additionally produced several additional versions of BASIC for MS-DOS/PC DOS including IBM Disk BASIC (BASIC D), IBM BASICA (BASIC A), GW-BASIC (a BASICA-compatible version that didn't need IBM's ROM) and QBasic, all typically bundled with the machine. In addition they produced the Microsoft BASIC Compiler aimed at professional programmers. Turbo Pascal-publisher Borland published Turbo Basic 1.0 in 1985 (successor versions are still being marketed by the original author under the name PowerBASIC). Microsoft wrote the windowing-based AmigaBASIC that was supplied with version 1.1 of the pre-emptive multitasking GUI Amiga computers (late 1985 / early 1986), although the product unusually didn't bear any Microsoft marks. These languages introduced a large number of extensions to the original home-computer BASIC, such as improved string manipulation and graphics support, access to the file system and additional data types. More important were the facilities for structured programming, including additional control structures and proper subroutines supporting local variables. Notwithstanding by the latter half of the 1980s, users were increasingly using pre-made applications written by others, rather than learning programming themselves, while professional programmers now had a wide range of more advanced languages available on small computers. C and later C++ became the languages of choice for professional "shrink wrap" application development.

Visual Basic

BASIC's fortunes reversed once again with the introduction in 1991 of Visual Basic ("VB") by Microsoft. This was an evolutionary development of QuickBasic, and included constructs from additional languages such as block structured control statements including "With" and "For Each", parameterized subroutines, optional static typing, and a full object oriented language. But the language retained considerable links to its past, such as the Dim statement for declarations, "Gosub"/Return statements, and even line numbers which were still needed to report errors properly. An important driver for the development of Visual Basic was as the new macro language for Microsoft Excel, a spreadsheet program. Ironically, given the origin of BASIC as a "beginner's" language, and apparently even to the surprise of a large number of at Microsoft who still initially marketed it as a language for hobbyists, the language had come into widespread use for small custom business applications shortly after the release of VB version 3.0, which is widely considered the first relatively stable version. While a large number of advanced programmers still scoffed at its use, VB met the needs of small businesses efficiently wherever processing speed was less of a concern than ease of development.

By that time, computers running Windows 3.1 had become fast enough that a large number of business-related processes can be completed "in the blink of an eye" even using a "slow" language, as long as large amounts of data weren't involved. Many small business owners found they could create their own small, yet useful applications in a few evenings to meet their own specialised needs. Eventually, throughout the lengthy lifetime of VB3, knowledge of Visual Basic had become a marketable job skill. Microsoft additionally produced VBScript in 1996 and Visual Basic .NET in 2001. The latter has essentially the same power as C# and Java but with syntax that reflects the original Basic language.

Three modern Basic variants: Mono Basic, OpenOffice.org Basic and Gambas

Post-1990 versions and dialects

Many additional BASIC dialects have additionally sprung up after 1990, including the open source QB64 and FreeBASIC, inspired by QBasic, and the Visual Basic-styled RapidQ, Basic For Qt and Gambas. Modern commercial incarnations include PureBasic, PowerBASIC, Xojo, Monkey X and True BASIC (the direct successor to Dartmouth BASIC from a company controlled by Kurtz). Several web-based simple BASIC interpreters additionally now exist, including and Microsoft's Small Basic (educational software). Versions of BASIC have been showing up for use on smartphones and tablets. Apple App Store contains such implementations of BASIC programming language as smart BASIC, Basic!, HotPaw Basic, BASIC-II, techBASIC and others. Android devices feature such implementations of BASIC as RFO BASIC and Mintoris Basic. Applications for a few mobile computers with proprietary OS (CipherLab) can be built with programming environment based on BASIC. An application for the Nintendo 3DS and Nintendo DSi called Petit Computer allows for programming in a slightly modified version of BASIC with DS button support. A 3DS sequel was released in Japan in November 2014.

Calculators

Variants of BASIC are available on graphing and otherwise programmable calculators made by Texas Instruments, HP, Casio, and others.

Windows command line

QBasic, a version of Microsoft QuickBasic without the linker to make EXE files, is present in the Windows NT and DOS-Windows 95 streams of operating systems and can be obtained for more recent releases like Windows 7 which don't have them. Prior to DOS 5, the Basic interpreter was GW-Basic. QuickBasic is part of a series of three languages issued by Microsoft for the home and office power user and small scale professional development; QuickC and QuickPascal are the additional two. For Windows 95 and 98, which don't have QBasic installed by default, they can be copied from the installation disc, which will have a set of directories for old and optional software; additional missing commands like Exe2Bin and others are in these same directories.

Other

BASIC came to a few video game systems, like the Nintendo Famicom.

The various Microsoft, Lotus, and Corel office suites and related products are programmable with Visual Basic in one form or another, including LotusScript, which is quite similar to VBA 6. The Host Explorer terminal emulator uses WWB as a macro language; or more recently the programme and the suite in which it is contained is programmable in an in-house Basic variant known as Hummingbird Basic. The VBScript variant is used for programming web content, Outlook 97, Internet Explorer, and the Windows Script Host. WSH additionally has a Visual Basic for Applications(VBA) engine installed as the third of the default engines along with VBScript, JScript, and the numerous proprietary or open source engines which can be installed like PerlScript, a couple of Rexx-based engines, Python, Ruby, Tcl, Delphi, XLNT, PHP, and others; meaning that the two versions of Basic can be used along with the additional mentioned languages, as well as LotusScript, in a WSF file, through the component object model, and additional WSH and VBA constructions. VBScript is one of the languages that can be accessed by the 4Dos, 4NT, and Take Command enhanced shells SaxBasic and WWB are additionally quite similar to the Visual Basic line of Basic implementations. The pre-Office 97 macro language for Microsoft Word is known as WordBasic. Excel 4 and 5 use Visual Basic itself as a macro language. Many Linux distributions include Chipmunk Basic, an old school interpreter similar to BASICs of the 1970s. Chipmunk Basic is additionally available for Microsoft Windows and OS X.

Nostalgia

The ubiquity of BASIC interpreters on personal computers was such that textbooks once included simple "Try It In BASIC" exercises that encouraged students to experiment with mathematical and computational concepts on classroom or home computers. Popular computer magazines of the day typically included type-in programs. Futurist and sci-fi writer David Brin mourned the loss of ubiquitous BASIC in a 2006 Salon article as have others who first used computers throughout this era. In turn, the article prompted Microsoft to develop and release Small Basic. Dartmouth held a fiftieth anniversary celebration for BASIC on 1 May 2014 as did additional organisations; at least one organisation of VBA programmers organised a 35th anniversary observance in 1999.

Syntax

Typical BASIC keywords

Data manipulation
  • LET: assigns a value (which might be the result of an expression) to a variable.
  • DATA: holds a list of values which are assigned sequentially using the READ command.
Program flow control
  • IF ... THEN ... ELSE: used to perform comparisons or make decisions.
  • FOR ... TO ... {STEP} ... NEXT: repeat a section of code a given number of times. A variable that acts as a counter is available within the loop.
  • WHILE ... WEND and REPEAT ... UNTIL: repeat a section of code while the specified condition is true. The condition might be evaluated before each iteration of the loop, or after.
  • DO ... LOOP {WHILE} or {UNTIL}: repeat a section of code Forever or While/Until the specified condition is true. The condition might be evaluated before each iteration of the loop, or after.
  • GOTO: jumps to a numbered or labelled line in the program.
  • GOSUB: jumps to a numbered or labelled line, executes the code it finds there until it reaches a RETURN Command, on which it jumps back to the operator following the GOSUB - either after a colon, or on the next line. This is used to implement subroutines.
  • ON ... GOTO/GOSUB: chooses where to jump based on the specified conditions. See Switch statement for additional forms.
  • DEF FN: a pair of keywords introduced in the early 1960s to define functions. The original BASIC functions were modelled on FORTRAN single-line functions. BASIC functions were one expression with variable arguments, rather than subroutines, with a syntax on the model of DEF FND(x) = x*x at the beginning of a program. Function names were originally restricted to FN+one letter.
Input and output
  • LIST: displays all inputted code.
  • PRINT: displays a message on the screen or additional output device.
  • INPUT: asks the user to enter the value of a variable. The statement might include a prompt message.
  • TAB or AT: sets the position where the next character will be shown on the screen or printed on paper.
Miscellaneous
  • REM: holds a programmer's comment or REMark; often used to give a title to the programme and to help identify the purpose of a given section of code.
  • USR: transfers programme control to a machine language subroutine, usually entered as an alphanumeric string or in a list of DATA statements.
  • TRON: turns on a visual, screen representation of the flow of BASIC commands by displaying the number of each command line as it is run. The TRON command, largely obsolete now, stood for, TRace ON. This meant that command line numbers were displayed as the programme ran, so that the command lines can be traced. This command allowed easier debugging or correcting of command lines that caused problems in a program. Problems included a programme terminating without providing a desired result, a programme providing an obviously erroneous result, a programme running in a non-terminating loop, or a programme otherwise having a non-obvious error.
  • TROFF: turns off the display of the number of each command line as command lines run after the command TRON has been used.

Data types and variables

Minimal versions of BASIC had only integer variables and one- or two-letter variable names, which minimised requirements of limited and expensive memory (RAM). More powerful versions had floating-point arithmetic, and variables can be labelled with names six or more characters long. There were a few problems and restrictions in early implementations; for example, Applesoft allowed variable names to be several characters long, but only the first two were significant, thus it was possible to inadvertently write a programme with variables "LOSS" and "LOAN", which would be treated as being the same; assigning a value to "LOAN" would silently overwrite the value intended as "LOSS". Keywords couldn't be used in variables in a large number of early BASICs; "SCORE" would be interpreted as "SC" OR "E", where OR was a keyword. String variables are usually distinguished in a large number of microcomputer dialects by having $ suffixed to their name, and values are often identified as strings by being delimited by "double quotation marks". Arrays in BASIC could contain integers, floating point or string variables.

Some dialects of BASIC supported matrices and matrix operations, useful for the solution of sets of simultaneous linear algebraic equations. These dialects would directly support matrix operations such as assignment, addition, multiplication (of compatible matrix types), and evaluation of a determinant. Many microcomputer BASICs didn't support this data type; matrix operations were still possible, but had to be programmed explicitly on array elements.

Examples

Unstructured BASIC

The original Dartmouth Basic was unusual in having a matrix keyword, MAT. Although dropped by most later microprocessor derivatives it is used in this example from the 1968 manual which averages the numbers that are input:

5 LET S = 0 10 MAT INPUT V 20 LET N = NUM 30 IF N = 0 THEN 99 40 FOR I = 1 TO N 45 LET S = S + V(I) 50 NEXT I 60 PRINT S/N 70 GO TO 5 99 END

New BASIC programmers on a home computer might start with a simple program, perhaps using the language's PRINT statement to display a message on the screen; a well-known and often-replicated example is Kernighan and Ritchie's Hello world program:

10 PRINT "Hello, World!"20 END

An infinite loop can be used to fill the display with the message.

Most first-generation BASIC versions such as MSX BASIC and GW-BASIC supported simple data types, loop cycles and arrays. The following example is written for GW-BASIC, but will work in most versions of BASIC with minimal changes:

10 INPUT "What is your name: "; U$20 PRINT "Hello "; U$30 INPUT "How a large number of stars do you want: "; N40 S$ = ""50 FOR I = 1 TO N60 S$ = S$ + "*"70 NEXT I80 PRINT S$90 INPUT "Do you want more stars? "; A$100 IF LEN(A$) = 0 THEN GOTO 90110 A$ = LEFT$(A$, 1)120 IF A$ = "Y" OR A$ = "y" THEN GOTO 30130 PRINT "Goodbye "; U$140 END

The resulting dialogue might resemble:

What is your name: MikeHello MikeHow a large number of stars do you want: 7*******Do you want more stars? yesHow a large number of stars do you want: 3***Do you want more stars? noGoodbye Mike

Structured BASIC

Second-generation BASICs (for example, VAX Basic, SuperBASIC, True BASIC, QuickBASIC, BBC BASIC, Pick BASIC and PowerBASIC) introduced a number of features into the language, primarily related to structured and procedure-oriented programming. Usually, line numbering is omitted from the language and replaced with labels (for GOTO) and procedures to encourage easier and more flexible design. In addition keywords and structures to support repetition, selection and procedures with local variables were introduced.

The following example is in QuickBASIC:

DECLARE SUB PrintSomeStars (StarCount!)REM QuickBASIC exampleINPUT "What is your name: ", UserName$PRINT "Hello "; UserName$DO   INPUT "How a large number of stars do you want: ", NumStars   CALL PrintSomeStars(NumStars)   DO      INPUT "Do you want more stars? ", Answer$   LOOP UNTIL Answer$ <> ""   Answer$ = LEFT$(Answer$, 1)LOOP WHILE UCASE$(Answer$) = "Y"PRINT "Goodbye "; UserName$ENDSUB PrintSomeStars (StarCount)   REM This procedure uses a local variable called Stars$   Stars$ = STRING$(StarCount, "*")   PRINT Stars$END SUB

BASIC with object-oriented features

Third-generation BASIC dialects such as Visual Basic, Xojo, StarOffice Basic and BlitzMax introduced features to support object-oriented and event-driven programming paradigm. Most built-in procedures and functions are now represented as methods of standard objects rather than operators. Also, the Operating System became more and more available to the BASIC language.

The following example is in Visual Basic .NET:

Public Class StarsProgram   Public Shared Sub Main()      Dim UserName, Answer, stars As String, NumStars As Integer      Console.Write("What is your name: ")      UserName = Console.ReadLine()      Console.WriteLine("Hello {0}", UserName)      Do         Console.Write("How a large number of stars do you want: ")         NumStars = CInt(Console.ReadLine())         stars = New String("*", NumStars)         Console.WriteLine(stars)         Do            Console.Write("Do you want more stars? ")            Answer = Console.ReadLine()         Loop Until Answer <> ""         Answer = Answer.Substring(0, 1)      Loop While Answer.ToUpper() = "Y"      Console.WriteLine("Goodbye {0}", UserName)   End SubEnd Class

Standards

  • ANSI/ISO/IEC Standard for Minimal BASIC:
    • ANSI X3.60-1978 "For minimal BASIC"
    • ISO/IEC 6373:1984 "Data Processing — Programming Languages — Minimal BASIC"
  • ECMA-55 Minimal BASIC (withdrawn, similar to ANSI X3.60-1978)
  • ANSI/ISO/IEC Standard for Full BASIC:
    • ANSI X3.113-1987 "Programming Languages Full BASIC"
    • INCITS/ISO/IEC 10279-1991 (R2005) "Information Technology - Programming Languages - Full BASIC"
  • ANSI/ISO/IEC Addendum Defining Modules:
    • ANSI X3.113 Interpretations-1992 "BASIC Technical Information Bulletin # 1 Interpretations of ANSI 03.113-1987"
    • ISO/IEC 10279:1991/ Amd 1:1994 "Modules and Single Character Input Enhancement"
  • ECMA-116 BASIC (withdrawn, similar to ANSI X3.113-1987)