Logo

Logo gave children a creature to program. Type FORWARD 100 and the turtle walks forward, drawing a line behind it; type RIGHT 90 and it turns on the spot. To draw a square, a child could walk one out on the floor and then tell the turtle to do the same. The language behind it was far more than a drawing toy. It descended from Lisp, the language of artificial-intelligence research, and it could handle words, lists and recursion.

Logo began in 1967 at Bolt Beranek and Newman (BBN), a research firm in Cambridge, Massachusetts, where Wally Feurzeig led the team and Seymour Papert and Cynthia Solomon worked with him. Feurzeig also gave it its name, from the Greek logos, “word” or “thought”. Through the 1970s it was developed mainly by Papert’s Logo Group at MIT. In the early 1980s it reached home computers and classrooms on both sides of the Atlantic.

Fast facts

• Created: 1967 at BBN, Cambridge, Massachusetts. Some accounts, including Harold Abelson’s TI Logo (1984), give 1968.
• Designers: Wally Feurzeig, Seymour Papert and Cynthia Solomon.
• Developed: at MIT’s Artificial Intelligence Laboratory and its Division for Study and Research in Education, and at BBN and the University of Edinburgh.
• Ancestry: Lisp.
• Best known for: turtle graphics.
• Home versions: TI Logo (1981), Apple Logo (1982), Atari Logo (1983), Commodore 64 Logo, Sinclair Logo (1984), and four rival Logos for the BBC Micro by 1985.

No threshold, no ceiling

Abelson, a member of the MIT Logo Group, summed up the aim in 1984: “Logo’s designers are guided by the vision of an educational tool with no threshold and no ceiling.” A beginner should be able to start at once, and there should be no point at which the language stopped them. Mitchel Resnick and his colleagues later restated it in their paper on Scratch: “Papert argued that programming languages should have a ‘low floor’ (easy to get started) and a ‘high ceiling’”. Resnick’s group added a third idea of their own, “wide walls”, for the variety of projects a language should support.

Papert set out the thinking behind it for a general audience in Mindstorms: Children, Computers and Powerful Ideas (1980). By 1984 Sinclair User’s Theo Wood, reporting from the British Logo Users Group conference, called the book “the Bible of Logo enthusiasts”.

The turtle

The first turtles were robots. “Early MIT versions of Logo actually controlled a floor robot that resembled a turtle,” BYTE explained in 1981, and working with the floor turtle “seemed to facilitate the transition to using the screen turtle”. On screen the turtle became a small triangle, but the commands stayed the same:

REPEAT runs a list of commands several times, and TO teaches the turtle a new word. Abelson’s TI Logo opens with this procedure:

TO SQUARE
REPEAT 4 [FORWARD 100 RIGHT 90]
END

Once SQUARE is defined it works like any built-in command, so REPEAT 36 [SQUARE RIGHT 10] draws 36 squares, each turned a little further, in a flower-like pattern. Procedures can call themselves, and Logo’s teachers used the turtle to introduce recursion as well as geometry.

Logo on home computers

Logo reached home computers from 1981. In 1979 the MIT Logo Group and Texas Instruments began work on a version for the TI-99/4, which appeared as TI Logo in 1981. For the Apple II there were several: in December 1982 SoftSide reviewed Apple Logo, “written by LOGO Computer Systems in Quebec and sold by Apple” for $175, alongside MIT Logo sold by Krell Software and by Terrapin for $150 each. Logo Computer Systems Inc. (LCSI) went on to write Atari Logo, a 16K cartridge selling for $99.95 in 1983, and ANTIC found it bore “an extremely close resemblance” to the Apple version. Terrapin wrote Commodore’s Logo for the 64.

In Britain, Sinclair Logo for the 48K Spectrum came out in September 1984, on cassette with two books, at £39.95. Sinclair User reported that it was “of the original Logo designed by Seymour Papert and developed by Logo Computer Systems”.

The BBC Micro, the machine most British schools bought, had no full Logo until the start of 1985, and then it had four. In May 1985 Acorn User compared “the big four”: Logotron Logo, written by LCSI and its partner SOLI and supplied on a 16K ROM; Acornsoft Logo, written in BCPL by Chris Jobson and John Richards; LSL Logo, which had grown out of a feasibility study for the Department of Industry; and Open Logo, from the Open University and BBC Publications. Three cost £59.95 and Open Logo £69.95. The reviewer, Joe Telford, found “no outright overall winner in the battle of the turtles”.

Turtles in British classrooms

Floor turtles came back with the micros. Acorn User in November 1984 surveyed the robots available to schools. The first commercial ones came from Jessop Microelectronics: the Jessop or “Edinburgh” turtle, developed at the University of Edinburgh’s Department of Artificial Intelligence, which had been one of Logo’s research centres. The Valiant Turtle, a battery-powered robot controlled by infra-red, “was launched in July this year—in the House of Commons, of all places!” It cost more than £170.

Logo was already in British primary schools by then. In December 1982 Acorn User carried a teacher’s account of using it with children in Croydon, on a BBC Micro bought under the Department of Industry’s scheme to subsidise computers for primary schools.

After the 1980s

Logo kept changing after its home-computer years, as the Logo Foundation’s history records. LCSI’s LogoWriter added word processing, and LEGO/Logo, developed at the MIT Media Lab, let children program motors and sensors built from LEGO. LCSI’s MicroWorlds followed in 1993, Resnick’s StarLogo in 1994, and later Uri Wilensky’s NetLogo. Papert’s name went on to LEGO’s Mindstorms robot kits.

Scratch, launched by Resnick’s Lifelong Kindergarten group at the MIT Media Lab in May 2007, replaced typed commands with blocks, but its designers described it as a response to Logo and to what Logo had not achieved. Python’s standard library still includes a turtle module, which its documentation describes as “an implementation of the drawing tools introduced in Logo”. Seymour Papert died on 31 July 2016, aged 88.

Released source code

The source code of several early Logo implementations has been published in the PDP-10 ITS archive on GitHub, including BBN’s PDP-10 Logo and MIT’s CLOGO, 11LOGO and APLOGO, MIT’s Logo for the Apple II. The source code of LCSI’s commercial versions has not been published.

See also

• Seymour Papert
• BBC Micro
• Apple II
• ZX Spectrum
• Scratch