Harbour New Data types

Data type & Syntax extensions in Harbour

In addition to Clipper’s scalar ( Character, Number, Date, Logical, MEMO, Nil ) and complex ( array, CodeBlock )  data types; Harbour has extended data types: pointer as scalar and object and hach as complex type.

For standard data types please refer here and/or here.

In database files (tables) data types of fields are predefined in structure of table.

For extended field types please refer here.

For data items other than fields (such as variables and manifest constants); in general, type of data  determined automatically by system, when assigning a value. The first basic way of this, is assigning a “literal” value.

For a working sample about constants please refer here.

cString := "This is a string" // A character string enclosed by a string delimiter
nNumber := 123.45 // A numeric value combined digits, decimal point and a sign ( + / - )
lTrue   := .T. // A T (tYy) or F (fNn) letter enclosed by two periods (.)
aArray  := {} // Arrays can be assigned literally by enclosed with curly brace

In addition to this basic literal value notations, Harbour has also extended notations:

– Data Types determined by special prefixs

— 0x… : Hexadecimal constant

  nNumber := 0x0A  // 0x prefix implies the string as Hexadecimal String  
                   // and type of resulting value become as Numeric (N) 
  ? nNumber, VALTYPE( nNumber ) // 10 N

— 0d… date constant

    dDate_1 := 0d20121225  // 0d prefix implies the string a date string 
                           // ( instead of using CTOD() )
                           // and type of resulting value become as Date (D) 
    ? dDate_1, VALTYPE( dDate_1 ) // 25.12.2012 D

– Special literal string formats

— d”…” : Date constant

dDate_2 := d"2012-12-26" ? dDate_2, VALTYPE( dDate_2 ) // 26.12.2012 D

— t”…” : Time constant

tTime_1 := dDate_2 + t”01:31:06″

? tTime_1, VALTYPE( tTime_1 ) // 26.12.2012 01:31:06.000 T

— e”…” : Escape sequences

Escape sequences are used to define certain special characters within string literals.

( Prefix by “\” escape sequence codes within that string )

The following escape sequences are available in C and C++ language :

sequence Description            Representation

   '     single quote          byte 0x27
   "     double quote          byte 0x22
   ?     question mark         byte 0x3f
         backslash             byte 0x5c

         null character        byte 0x00
   a     audible bell          byte 0x07
   b     backspace             byte 0x08
   f     form feed - new page  byte 0x0c
   n     line feed - new line  byte 0x0a
   r     carriage return       byte 0x0d
   t     horizontal tab        byte 0x09
   v     vertical tab          byte 0x0b

   nnn   arbitrary octal value byte nnn
   xnn   arbitrary hexadecimal value byte nn

   unnnn arbitrary Unicode value.
          May result in several characters. code point U+nnnn
   Unnnnnnnn arbitrary Unicode value.
           May result in several characters. code point U+nnnnnnnn

Note that all sequences not available in Harbour.

For the new complex data type Hash, there is a literally assigning way :

hHash := { => }    // => sign indicates the hash



* Data Types determined by special prefixs

** 0x... : Hexadecimal constant

nNumber := 0x0A // 0x prefix implies the string as Hexadecimal String 
// and type of resulting value become as Numeric(D)
? nNumber, VALTYPE( nNumber ) // 10 N
** 0d... date constant 

 dDate_1 := 0d20121225 // 0d prefix implies the string a date string 
                       // ( instead of using CTOD() )
                       // and type of resulting value become as Date (D) 

? dDate_1, VALTYPE( dDate_1 ) // 25.12.2012 D
* Special literal string formats
** d"..." : Date constant
dDate_2 := d"2012-12-26"
? dDate_2, VALTYPE( dDate_2 ) // 26.12.2012 D 

** t"..." : Time constant
tTime_1 := dDate_2 + t"01:31:06"
? tTime_1, VALTYPE( tTime_1 ) // 26.12.2012 01:31:06.000 T

** e"..." : Escape sequences 

? e"This is\na string\nformatted by\nEscape sequences \x21

/* The result : 
This is
a string
formatted by
Escape sequences !
@ MAXROW(), 0 WAIT "EOF DTS_Exts.prg" 
RETURN // DTS_Exts.Main() 

*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DTS_Exts

The Clipper conversion process

The Clipper conversion process (.pdf)

Basic Controls – 2

( Text Box  )

We are continuing with Viva_HMG.hbp, Main.prg and Main.fmg. We have assign real actions other than MsgBox() to our two buttons now : Open File and Edit Record. Open File not required GUI controls ( at least for now ), so we can begin with it: For Open File we need a file ( a table ) first: it’s here; a table with four field: Clients.dbf :

No:  Field Name Type Width Dec
---  ---------  ---- ----- ---
  1  CLI_ID       N      5   0
  2  CLI_SNAM     C     12   0
  3  CLI_NAME     C     12   0
  4  CLI_TLF      C     11   0

And then add a little routine to Main.prg for open (USE) it:

      MsgStop( "Clients.dbf file not found !")
RETURN // OpenTable()

And assign this procedure to ACTION of  Open File  button.

Now, we can begin Edit Record task. For this task we need a separate form, a sub form.  Then let’s begin. “New form” from tool-bar and assign a name : EditReco. Assign a title : “Edit Record”, a type : MODAL. Our table has four fields, so we need four LABEL first:

Names :  lblCLI_ID,  lblCLI_SNAM,  lblCLI_NAME, lblCLI_TLF;

Values ( Captions ) : ID,  Surname, Name, Tlf

Rows : 60, 100, 140, 180 Col : 60

Cols :  60, 60, 60, 60

Widths : 70, 70,  70, 70


We can see our job at work:

Now we need a place  for display the current data and accept user input. The control for this purpose is text box. So we need to define four text boxes for each field in the table.

The button of text box in the IDE tool bar is :

Names :  txbCLI_ID,  txbCLI_SNAM,  txbCLI_NAME, txbCLI_TLF;

Rows : 55, 95, 135, 175

Col : 140

DataTypes : First : NUMERIC, others : CHARACTER

We can see our job at work:

Well …

But where are table data ?

To see table data we need assign field values to text boxes as values.

Again, a little procedure:

   EditReco.txbCLI_ID.Value   := CLIENTS->CLI_ID
   EditReco.txbCLI_SNAM.Value := CLIENTS->CLI_SNAM
   EditReco.txbCLI_NAME.Value := CLIENTS->CLI_NAME
   EditReco.txbCLI_TLF.Value  := CLIENTS->CLI_TLF
RETURN // ReadData()

and a call command for this procedure to ON INIT event of  EditReco form.

The result :

Everything is OK ?

No !

This is only first record of table; how we will see others ?

Yes, we need now yet another feature: navigation; that is travelling between records of table.

But before navigation, we have a problem: Open Table must be processed before Edit Record.

Otherwise a run time error will occurs: Alias does not exist. 

What we can do?

–       Discard Open Table button, open the table automatically; at beginning of program or at beginning of editing.

–       Before editing, check the table, if doesn’t open,

–          a)  open automatically or

–          b)  warn user and don’t load Edit Table form.

Probably most convenient is : disable Edit Record button until table is open.

First a mini procedure :

PROCEDURE Initialize()
   Main.btnEditRec.Enabled := .F.
RETURN // Initialize()

And then add this procedure ON INIT event of form main:

Last point: enable it after USE table:

      Main.btnEditRec.Enabled := .T.
      MsgStop( "Clients.dbf file not found !")
RETURN // OpenTable()

Run and see:

Before Open File :

After Open File:

Now we can pass to navigation:

We need seven buttons: Go Top, Go Next, Go Previous, Go Last, Save, Discard, Exit.

Name: btnGoTop, Caption : Top,  Col : 50, Row: 220, Height: 28, Width: 60

Name: btnGoNext, Caption : Next,  Col : 130, Row: 220, Height: 28, Width: 60

Name: btnPrevious, Caption : Previous,  Col : 200, Row: 220, Height: 28, Width: 60

Name: btnGoLast, Caption : Last,  Col : 270, Row: 220, Height: 28, Width: 60

Name: btnSave Caption : Save,  Col : 380, Row: 60, Height: 28, Width: 100

Name: btnDiscard, Caption : Discard,  Col : 380, Row: 140, Height: 28, Width: 100

Name: btnExit, Caption : Exit,  Col : 380, Row: 220, Height: 28, Width: 100

Common: Font Name: Tahoma, Font Size: 9

Actions :

btnGoTop: ( DBGOTOP(), ReadData() )
btnGoNext: ( DBSKIP(), ReadData() )
btnPrevious: ( DBSKIP( -1 ), ReadData() )
btnGoLast: ( DBGOBOTTOM(), ReadData() )
btnSave: SaveData()
btnDiscard: ReadData()

btnExit: ThisWindow.Release

Note that actions of four first buttons include two actions, separated by comma and enclosed by parenthesis.  With this notation we can define more than one action together.

SaveData() is the inverse of  ReadData(): copy values of text boxes to table fields.

PROCEDURE SaveData()         // Save data from text boxes to table
   CLIENTS->CLI_ID   := EditReco.txbCLI_ID.Value
   CLIENTS->CLI_SNAM := EditReco.txbCLI_SNAM.Value
   CLIENTS->CLI_NAME := EditReco.txbCLI_NAME.Value
   CLIENTS->CLI_TLF  := EditReco.txbCLI_TLF.Value
RETURN // SaveData()

Discard is simply re-reading data from table.

The result:

To be continued …

Download source files

Data Type Terms

Character :

A special data type consisting of one or more values in the extended character set. Characters can be grouped together to form strings. The maximum size of a character string In Clipper language is 65,534 bytes.

In Clipper, a character data may include any character, including “control” or “unprintable” characters, that are ASCII code less than 32.

Note : Characters with ASCII code 9, 10 and 13 always treated as “white spaces”; this important with EMPTY() and xTRIM() functions.

See Also:  String

Code Block :

A special data type that refers to a piece of compiled program code. In a program, the source code that specifies the creation of a code block.

Data Type :

The category of a data value. A data type is distinguished by the set of allowable values for that type, the set of operators that can be applied, and the storage format used to represent these values. In Clipper language, the following data types are defined: character, numeric, date, logical, array, object, code block, and NIL. Program variables may contain values of any type. Database field variables are limited to character, numeric, date, logical, and a special type called memo which is treated the same as character.

Date Type :

A special data type consisting of digits to store year, month, and day values. Operations on date values are based on chronological values.

Integer :

A number with no decimal digits. Note that Clipper language does not provide a separate data type for integer values.

Literal :

A source code element interpreted literally (as encountered), and assumed to have no abstract meaning. Generally a constant.

See Also: Constant

Logical Type :

A special data type consisting of true (.T.) or false (.F.) values.

See Also: Condition

Memo Type :

A special database field type consisting of one or more characters in the extended character set. The maximum size of a memo field in Clipper language is 65,534 bytes. A memo field differs only from a character string by the fact it is stored in a separate memo (.DBT file) and the field length is variable-length.

See Also: Character String


A special data type that has only one allowable value. The special value (NIL) is automatically assigned to all uninitialized variables except publics, and is also passed as a substitute when arguments are omitted in a procedure or function call.

Numeric Type :

A special data type consisting of values that indicate magnitude. Numeric values consist of digits between zero and nine, a sign, and a decimal point.

Objects :

An object is an instance of a class. Each object has one or more attributes (called instance variables) and a series of operations (methods) that execute when a message is sent to the object. The object’s instance variables can only be accessed or assigned by sending messages to the object. Objects are created by calling a special function associated with a class.

See Also: Classes, Instance Variables, Messages, Methods

String :

Generically, a value of type character. In source code, a series of characters enclosed in single or double quotes.

See Also : Character

Substring :

A string within a string, usually to be specified as an argument of a function or command.

Clipper characteristics

Clipper, characteristics and versions

Clipper is procedural and imperative Programming language created in 1985 by Nantucket Corporation and sold later to Computer Associates, the one commercialized that it like CA-Clipper. At first Clipper was created as Compiler for the managing system interpreter of data bases dBase III (in fact seasonal versions of Nantucket included a label indicated that it thus), but with time the product evolved and matured, becoming a compiled language more powerful than the original one, not only by its own implementations but also by the extensions developed by third parties in C, Assembly and Pascal, of which it was inheriting characteristic. This turned into the tool leader of development of applications of relational databases under operating system MSDOS, mainly programs of management, accounting and invoicing ( SAGE – SP, leader of the Spanish market, uses for Contaplus and FacturaPlus ), commercial agendas and programs of pricing (approximately 80% of the insurance agencies of Spain used it in the programs of their agents).


Unlike other x-Base languages, Clipper never counted on a way Interpreter, similar to the one of dBase . Its utilities for handling of Base of data, such as the one of creation of tables (DBF), they gave with the source code written in Clipper and including, the user could adapt them to his needs if he wanted. They also contributed to many routines written in C and Assembly to which the user could go, to extend and even to create libraries of pre-connects complete.

Clipper works in way pure Compiler generating an object code binary; the package also provided a connector (RTLINK or DLINK) that with the object module and the libraries of pre-connects generated ejecuble a module direct. This last one granted to the Clipper applications a speed to him that other managers of data bases did not own, and, like disadvantage, the necessity to recompilar and to connect again whenever some error in the source code was corrected ( Purification was slow).

It owns characteristics that were very attractive for their time and its surroundings of work (TWO), such as: own handling of Virtual memory ( ram in disc); handling of extended memory, the applications could overcome the barrier of 640Kb of ram imposed by MSDOS ; routines and libraries can be only loaded when they are necessary and they unload of ram when no longer they make lack (it connects and overlays dynamic); the amount of registries by tables only was limited the capacity of the disc; great robustness in the applications, particularly in the designed ones for client-servant (network LAN), etc.

Although it did not own practically calculation functions such as the trigonometrical ones, that other languages like FoxPro if they incorporated; the user them could easily elaborate in C and use them like any other function of own bookstore of the package, advantage that happened of which the Clipper compiler and many of their libraries were almost completely developed in C .

Its form, administration, storage and interchange of screens were simple, effective and quick; what good dynamism to the applications developed with Clipper granted.

The language in if he were powerful, counting with a great amount of sentences, functions, memory management and variables that allowed to the programmer very flexible and efficient developments; in reasonably fast form. Also the package included complete “manual in line navegable”, that ram was loaded in memory, to requirement of the programmer, and it was acceded by the single pressure of a pair of keys.

At his long time sea bream, it has been, probably, the language relational database manager of ” low and medium porte” more used in the world. Today many Clipper developers even exist (some grouped communities and with forums in Internet), that make applications, style Windows, even using their own graphical libraries written in C and Assembly .

The first versions

The first versions denominate seasonal versions to make reference to a station of the year in their official names. All of them name like dBASE compilers . These were:

  • Nantucket Clipper Winter’84 – sent 25 of May of 1985
  • Nantucket Clipper Summer’85 – sent in 1985
  • Nantucket Clipper Winter’85 – sent 29 of January of 1986
  • Nantucket Clipper Fall’86 – sent 31 of October of 1986
  • Nantucket Clipper Summer’87 – sent 21 of December of 1987
  • Gatsoft Clipper Summer’88 – sent 16 of March of 1988

Clipper 5

Clipper 5.0 supposes a qualitative jump of the language, although it begins bad. Given the increasing popularity (Summer 87 has been used until the year 2000 like development tool), it is decided to concentrate more in extending the language that in being improved compiler of dBase. They are implemented therefore pseudo-objects and other improvements… but the product sends with numerous bugs that make that the objective public dissuades itself and continues using the Summer87 version, much more stable. The 5,01 correct many of the problems, but it will not be until the 5,2 that take place upsets massive of the developers.

Versions 5 of Nantucket are:

  • Nantucket Clipper 5,00 – sent in 1990
  • Nantucket Clipper 5,01 – sent 15 of April of 1991
  • Nantucket Clipper 5,01 Rev.129 – sent 31 of March of 1992

The American multinational Computer Associates acquires Nantucket and it is sent to improve the product strengthening the inherited characteristics of C, in particular the data type code-block (literally code block, a hybrid between macros of dBase, the evaluation of chains of characters and the leaders of functions). Another one of the improvements coming from version 5.0 is the system “Replaceable Drivers” Database; (RDD or basic drivers replacable of data), that allows with a single sentence to change between different basic norms from data. The appearance of version 5.2, with a frenetic race of subversions (with improvements and correction of errors) until 5.2c, that marks the beginning of the massive migration of those who still remained in Summer’87. The version of used Clipper of history happens more therefore. Contrary, her successor, 5,3, in spite of implementing improvements, falls in a bulk error, when not considering the compatibility with at least the most popular libraries of Clipper (as much commercial as freeware), and to consume excessive resources of TWO.

  • CA Clipper 5.01a –
  • CA Clipper 5,20 – sent 15 of February of 1993
  • CA-Clipper 5.2a – sent 15 of March of 1993
  • CA Clipper 5.2b – sent 25 of June of 1993
  • CA-Clipper 5.2c – sent 6 of August of 1993
  • CA Clipper 5.2d – sent 25 of March of 1994
  • CA-Clipper 5.2e – sent 7 of February of 1995
  • CA Clipper 5,30 – sent 26 of June of 1995
  • CA Clipper 5.3a – sent 20 of May of 1996
  • CA Clipper 5.3b – sent 20 of May of 1997

Computer Associates decides to leave Clipper before the might of Microsoft Windows, and overturns part of the development of Clipper ( project Reels of Nantucket) to its new tool CA-Line of vision Objects, that appears at the same time as 5.3 almost Clipper but the abandonment of the syntax x-Base and not to provide a tool with adapted migration, together with the high price of the product (that in addition debia to compete with other products of the own house, one of them based on BASIC ), causes that the thickness of Clipper programmers chooses to remain in versions 5.3 with libraries of third parties like FiveWin, or migrate to tools x-Base like Visual FoxPro as market TWO is reduced.

22 of April of 2002 Computer Associates and GrafX Software announces that they have reached an agreement of licensing, marketing and development of two of its languages of development: CA-Clipper and CA-Line of vision Objects.

One of the main characteristics that helped the success of Clipper was the possibility of expanding the language with routines in C and ensablador. Several of them, as CodeBase or Apollo is RDDs. With the appearance of Windows several of them were developed to carry the Clipper applications to Windows. Most popular she is the FiveWin Spanish, employee in products leaders of accounting in Spain.

In addition, the use of linkers alternative allowed to improve the generated yield of the feasible one. The most acclaimed it was Blinker, that adds a extensor of with TWO protected mode (it is used with numerous languages and compilers). It added support to compile programs and libraries for Windows.

At present the Clipper language is actively being implemented and being extended by several projects and salesmen. Between the projects of free Software we can emphasize Paper clip, Harbor and XHarbour . Between the commercial compilers XBase++ and Visual FlagShip. And Other products like ” MEDIATOR” that they offer the possibility him of connecting itself to relational Database servers like MS-SQL, MySQL and Oracle.

XBase++ has been called the Clipper Compiler of 32 bits, being at the moment the leader in innovations and incorporations to the language. Or they have been sold more than 25,000 copies of the compiler and they use from solitary developers to great companies like Hewlett-Packard or the Government of Canada.

Several of those implementations are portable thanks to their development in C ( TWO, Windows, Linux (32 and 64 bits), Unix (32 and 64 bits), and Mac OS X ), supporting several extensions of the language; they count on several extensions of the language, and several Replaceable Drivers Database (RDD) that the most popular formats of tables support, like DBF, DBTNTX, DBFCDX ( FoxPro and Comix), MachSix (Apollo), SQL, and more. All these new implementations maintain the complete compatibility with the standard x-Base sintax , at the same time as and syntax oriented to the destiny like SQLExecute()offer Object-oriented programming .

At the moment there is a free version, the Harbor Project that it has like original objective to be 100% compatible one with version 5.2 (most popular of the versions of Clipper), also are addition new characteristic like support for SQL through SQLite. Harbor is available for multiple platforms, including not only MSDOS and Windows, but also to Linux, OS/2 and others. In the month of August of the 2008 the launching of version 1.0 announced officially.

In 2005, Newsgroup of Usenet regarding Clipper comp.clipper and comp.visual-objects follow assets.

Programming in Clipper

Simple Hello world :

? ” Hello World! “

A simple mask of entrance of Base of data :


clear screen
@  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


Note : This article Gathered from here.

What is Clipper ?

As a computer software term, the word “Clipper” has two meaning :

1- A programming language

2- A compiler

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

Clipper was originally released in 1985 as a compiler for dBASE III, a very popular database language at the time. Compiling dBASE code changes it from interpreted code, which must be interpreted every time each line of code is executed, to p-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. As a technical marketing ploy, the p-code was wrapped into object code (linkable .obj files) which gave the impression that it was compiled to native code. Clipper was created by Nantucket Corporation led by Barry ReBell (political) and Brian Russell (technical), and later sold to Computer AssociatesGrafX Software licensed CA-Clipper in 2002 from CA for ongoing marketing and distribution.

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.

After “swallow” Nantucket at 1992, CA published a few releases of Clipper Compiler, lastly 5.3a at  May 20, 1997. But most of Clipper programmer uses preferably 5.2e – released February 7, 1995.

Although remained a DOS as the compiler, Clipper continues to live as the programming language.

The Clipper language is being actively implemented and extended by multiple organizations/vendors, like xBase ++ from Alaska Software and FlagShip, as well as free(GPL-licensed) projects like Harbour and xHarbour.

Many of the current implementations are portable (DOSWindowsLinux (32- and 64-bit), Unix (32- and 64-bit), and Mac 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, Apollo and Comix), MachSix (SIx Driver and 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().

Version history

The various versions of Clipper compiler were:

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

  • Nantucket Clipper Winter’84 – released May 25, 1985
  • Nantucket Clipper Summer’85 – released 1985
  • Nantucket Clipper Winter’85 – released January 29, 1986
  • Nantucket Clipper Autumn’86 – released October 31, 1986
  • Nantucket Clipper Summer’87 – released December 21, 1987

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

and from Computer Associates; CA-Clipper 5

  • CA Clipper 5.01a –
  • CA Clipper 5.20 – released February 15, 1993
  • CA-Clipper 5.2a – released March 15, 1993
  • CA Clipper 5.2b – released June 25, 1993
  • CA-Clipper 5.2c – released August 6, 1993
  • CA Clipper 5.2d – released March 25, 1994
  • CA-Clipper 5.2e – released February 7, 1995
  • CA Clipper 5.30 – released June 26, 1995
  • CA Clipper 5.3a – released May 20, 1996
  • CA Clipper 5.3b – released May 20, 1997


Note: This post is based upon mainly a Wikipedia article :