Clipper (programming language)

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Clipper is a computer programming language that is used to create software programs that originally operated primarily under DOS. Although it is a powerful general-purpose programming language, it was primarily used to create database/business programs.

Clipper was originally created in 1985 as a compiler for dBASE III, a very popular database language at the time. Compiling dBASE code changes it from interpreted code (i.e., human-readable source code), which must be interpreted every time each line of code is executed, to p-code (or pseudo-code), which uses a Virtual Machine to process the compiled p-code. p-code is considerably faster, but still not as fast as the machine code generated by native compilers. Clipper was created by Nantucket Corporation, and later sold to Computer Associates. On April 22, 2002 Computer Associates and GrafX Software announced they had reached a Development, Licensing, and Marketing Agreement for two of their software development languages -- CA-Clipper and CA-Visual Objects.

As the product matured, it remained a DOS tool for many years, but added elements of the C programming language and Pascal programming language, as well as OOP, and the code-block data-type (hybridizing the concepts of dBase macros, or string-evaluation, and function pointers), to become far more powerful than the original. Nantucket's Aspen project later matured into the Windows native-code Visual Objects compiler.

As of 2006, the Clipper language is being actively implemented, and extended, by multiple organizations/vendors, free (GPL-licensed) like CLIP, Harbour, xHarbour, as well as commercial compilers like XBase++, and FlagShip.

Many of the current (2006) implementations are portable (DOS, Windows, Linux (32- and 64-bit), Unix (32- and 64-bit), and OS X), supporting many language extensions [1], and have greatly extended runtime libraries, as well as various Replaceable Database Drivers (RDD) supporting many popular database formats, like DBF, DBTNTX, DBFCDX (FoxPro and Comix), MachSix (Apollo), SQL, and more. These newer implementations all strive for full compatibility with the standard dBase/xBase syntax, while also offering OOP approaches and target-based syntax such as SQLExecute().

As of 2006, the Clipper Usenet newsgroups comp.lang.clipper and comp.lang.clipper.visual-objects are still active.

[edit] Programming in Clipper

A simple hello world - application:

? "Hello World!"

A simple data base input mask:

USE Customer SHARED NEW
cls
@  1, 0 SAY "CustNum" GET Customer->CustNum PICT "999999" VALID Customer->CustNum > 0
@  3, 0 SAY "Contact" GET Customer->Contact VALID !empty(Customer->Contact)
@  4, 0 SAY "Address" GET Customer->Address
READ

The various versions of Clipper were

From Nantucket Corporation; the "seasonal versions", billed as "dBase compilers"

From Nantucket Corporation; Clipper 5

  • Nantucket Clipper 5.00 - released 1990
  • Nantucket Clipper 5.01 - released April 15, 1991
  • Nantucket Clipper 5.01 Rev.129 - released March 31, 1992
A Clipper 5.2 manual cover.

and from Computer Associates; CA-Clipper 5

[edit] External links

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