Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 (Tek) 9/28/84 based on 9/17/84; site orca.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!tektronix!orca!andrew From: andrew@orca.UUCP (Andrew Klossner) Newsgroups: net.lang Subject: ANSI Basic Message-ID: <1385@orca.UUCP> Date: Thu, 7-Mar-85 22:57:25 EST Article-I.D.: orca.1385 Posted: Thu Mar 7 22:57:25 1985 Date-Received: Sun, 10-Mar-85 06:21:03 EST Organization: Tektronix, Wilsonville OR Lines: 135 This note is to clear up some of the confusion, expressed in recent articles here, about ANSI Basic. I am a member of the ANSI Basic standardization committee (ANSI X3J2) and just finished leading a project to implement this language on the Tektronix 6000 family of computers. (Micro-review: CPU is National 32016 or 32032; OS is extended 4.2BSD; great networking; I like it.) The ANSI Basic defining document is technically still a "draft proposal". It is in essentially its final form and is now undergoing the formalities of the transition to an ANSI standard. This should all be finished up in early 1986. The exact same document is on its way to becoming an ISO (International Standards Organization) standard *and* an ECMA (European Computer Manufacturers Assocation or something like that) standard, and the three standardization committees hold regular joint meetings to maintain this. The document is 320 pages long, much smaller than the PL/I standard. A capsule list of features is: the usual numeric and string data types (no integers); arrays; practically every structured programming construct ever invented (FOR/NEXT, DO/LOOP/EXIT DO, SELECT/CASE) and all the unstructured ones (GOTO, GOSUB, ON..GOTO); function and subroutine procedures but with a maximum nesting of two (there are "internal" and "external" procedures); a somewhat unwieldy I/O sublanguage that's an amalgam of many existing implentations; exception (runtime error) trapping; an optional graphics chapter based on GKS level 0b (optional because not everyone has a graphics device); an optional concurrency chapter that's very popular in Europe; an optional business arithmetic (BCD) chapter. As to language size, Touch Technologies (San Diego) wrote a strictly interpreted implementation for the VAX that fits in 80k -- and includes extensions to deal with database management. By contrast, the Tektronix implementation is a compiler wrapped up in an interactive environment that makes it look like an interpreter; it takes about 800k (isn't demand paging wonderful!) and is chock full of local extensions. True Basic, a variant of the standard from Drs. Kurtz and Kemeny at Dartmouth College (the original inventors of Basic), runs on the IBM PC and Macintosh and is available, together with a book, for just under $100 from Addison-Wesley. Watch for it in bookstores, as A-W is gearing up for a big marketing push. IBM has expressed an interest in distributing the PC version. The other implementation that I know about is being done by Olivetti in Italy. To deal with some specific net complaints: "Impossible to interpret." The folks at Touch Techologies would argue with that. It's easy to get this impression from a quick reading of the standard, though. What is actually there are restrictions to make it easy to both interpret and compile; for example, a program must have a corresponding NEXT statement lexically following each FOR statement. You could read that to require that an interpreter make a pre-scan of the program before beginning execution, but in fact there is no such requirement; you can issue a runtime error if you run out of program without finding the NEXT, or you can extend your language to define a specific meaning for a FOR without a NEXT. "Three ways to declare an array." There are only two ways. But you can change the size of an array dynamically during an array assignment or input, so this might have looked like a third way. The two ways are there because data objects in ANSI Basic have more attributes than just numeric/type and scalar/array; one is that you can declare a maximum size on your (variable-sized) strings, the default being an implementation-defined figure no less than 132. A DECLARE statement was introduced to allow all of these attributes to be specified in a single statement. The DIM statement was retained to make it easy to run existing Basic programs. "Five ways to denote a function, plus program chaining." There's the standard DEF which defines a function in a single line, e.g., DEF sin(x)=sqrt(1-cos(x)^2) There's FUNCTION and EXTERNAL FUNCTION to define multiple-line function bodies. There's SUB and EXTERNAL SUB to define subprograms. (FUNCTIONs and SUBprograms are reminiscent of the corresponding objects in Fortran, except that they can be internal.) I guess that makes five, but it doesn't seem excessive. Program chaining is something that most Basics have; it wouldn't have been reasonable not to specify a chain construct in the standard. "Concurrency (an option at least)." I don't see anything wrong with adding a chapter which says that, if an implementation chooses to add concurrency to the language, it would be nice if they would do so in this way so as to enhance portability. This chapter was written by implementors in Europe, and this concurrency is running robots in factories now. "Breaks 100 percent of all existing Basic programs, no matter how simple due to REQUIRED new syntax." The only new REQUIREments that I can think of are: 1) All arrays must be declared as such; you can't just start using an array. This seems reasonable in light of modern ideas about programming. A big reason for this was to disambiguate array expressions when the popular MAT statements were added to the language. 2) The standard requires that assignment statements begin with the keyword LET. I don't know of any implementations that didn't add the obvious enhancement and make LET optional. This was a religious issue in the committee. "Makes BCD (inefficient) floating point the standard to preserve precision, then doesn't bother to provide integers." You don't have to implement BCD to conform to the standard. We use an IEEE floating point chip. Integers weren't implemented because the complications to the language would have been massive. We tried a couple of times but couldn't get past the "keep it simple" partisans. Here's an example of the problem: how big are integers? Are they 16 bits, or 32 bits, or is it up the implementation? Don't leave it up to the implementation because I want my program port to all systems. 16 bits is no good because my VAX does integers in 32 bits; why penalize me? 32 bits is no good because my Z80 has to do a lot of work to support them and all I really need is 16 bits. An optional chapter on integer arithmetic will be forthcoming in a couple of years. I don't argue that ANSI Basic is the best of all programming languages. (I could work up an argument for Algol 68, though ...) The point of ANSI Basic is that it is a concensus. Most of the major manufacturers were represented, and, after many long years, we came to an agreement on a standard dialect of Basic to implement across several computers. Surely this isn't bad news. -- Andrew Klossner (decvax!tektronix!orca!andrew) [UUCP] (orca!andrew.tektronix@csnet-relay) [ARPA]