Sancho at 10:47, 6 September 2011

2011-09-06T10:47:38Z

Sancho at 07:49, 6 September 2011

2011-09-06T07:49:10Z

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{{DISPLAYTITLE:An Overview of an {{OOo}} Basic Program}}
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{{Documentation/BASICGuideTOC
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{{OOo}} Basic is an interpreter language. Unlike C++ or Delphi, the {{OOo}} Basic compiler does not create executable or self-extracting files that are capable of running automatically. Instead, you execute an {{OOo}} Basic program inside {{OOo}}. The code is first checked for obvious errors and then executed line by line.

=== Program Lines ===
The Basic interpreter's line-oriented execution produces one of the key differences between Basic and other programming languages. Whereas the position of hard line breaks in the source code of Java, C++, or Delphi programs is irrelevant, each line in a Basic program forms a self-contained unit. Function calls, mathematical expressions, and other linguistic elements, such as function and loop headers, must be completed on the same line that they begin on.

If there is not enough space, or if this results in long lines, then several lines can be linked together by adding underscores _. The following example shows how four lines of a mathematical expression can be linked:

LongExpression = (Expression1 * Expression2) + _
(Expression3 * Expression4) + _
(Expression5 * Expression6) + _
(Expression7 * Expression8)

{{Documentation/Note|The underscore must always be the last character in a linked line and cannot be followed by a space or a tab or a comment, otherwise the code generates an error.
}}

In addition to linking individual lines, in {{OOo}} Basic you can use colons to divide one line into several sections, so that there is enough space for several expressions. The assignments

a = 1
a = a + 1
a = a + 1

can be written as follows:

a = 1 : a = a + 1 : a = a + 1

=== Comments ===

In addition to the program code to be executed, an {{OOo}} Basic program can also contain comments that explain the individual parts of the program and provide important information that can be helpful at a later point.

{{OOo}} Basic provides two methods for inserting comments in the program code:

<ul>
<li>All characters that follow an apostrophe are treated as comments:

<source lang="oobas">
Dim A ' This is a comment for variable A
</source></li>
<li>The keyword <tt>Rem</tt>, followed by the comment:

<source lang="oobas">
Rem This comment is introduced by the keyword Rem.
</source></li></ul>

A comment usually includes all characters up to the end of the line. {{OOo}} Basic then interprets the following line as a regular instruction again. If comments cover several lines, each line must be identified as a comment:

<source lang="oobas">
Dim B ' This comment for variable B is relatively long
' and stretches over several lines. The
' comment character must therefore be repeated
' in each line.
</source>

=== Markers ===

A {{OOo}} Basic program can contain dozens, hundreds, or even thousands of '''markers''', which are names for variables, constants, functions, and so on. When you select a name for a marker, the following rules apply:

* Markers can only contain Latin letters, numbers, and underscores (_).
* The first character of a marker must be a letter or an underscore.
* Markers cannot contain special characters, such as ä â î ß.
* The maximum length of a marker is 255 characters.
* No distinction is made between uppercase and lowercase characters. The <tt>OneTestVariable</tt> marker, for example, defines the same variable as <tt>onetestVariable</tt> and <tt>ONETESTVARIABLE</tt>.<br/> There is, however, one exception to this rule: a distinction is made between uppercase and lowercase characters for UNO-API constants. More information about UNO is presented in [[EN/documentation/basic_guide/api_intro|Introduction to the {{OOo}} API]].

{{Documentation/Caution|The names of the Basic modules (by default Module1, Module2, etc) are known by Basic on a public [[EN/documentation/basic_guide/scope_of_variables|scope]]. You must avoid to have a marker of public [[EN/documentation/basic_guide/scope_of_variables|scope]] with the same name as one of the modules of the library.

Example : Suppose that in your Basic library you have a module named PrintDoc. You must not declare, in any module of your library, a Public variable or a Public constant, or a Sub, or a Function, named PrintDoc.

If you do have such collision, Basic may produce strange runtime error messages, or your Sub may not work.}}

{{Documentation/VBAnote|The rules for constructing markers are different in {{OOo}} Basic than in VBA. For example, {{OOo}} Basic only allows special characters in markers when using <tt>Option Compatible</tt>, since they can cause problems in international projects.}}

Here are a few examples of correct and incorrect markers:

<source lang="oobas">
Surname ' Correct
Surname5 ' Correct (number 5 is not the first digit)
First Name ' Incorrect (spaces are not permitted)
DéjàVu ' Incorrect (letters such as é, à are not permitted)
5Surnames ' Incorrect (the first character must not be a number)
First,Name ' Incorrect (commas and full stops are not permitted)
</source>

Enclosing a variable name in square brackets allows names that might otherwise be disallowed; for example, spaces.

<source lang="oobas">
Dim [First Name] As String 'Space accepted in square brackets
Dim [DéjàVu] As Integer 'Special characters in square brackets
[First Name] = "Andrew"
[DéjàVu] = 2
</source>

{{PDL1}}

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−	{{~~Documentation/~~Caution\|The names of the Basic modules (by default Module1, Module2, etc) are known by Basic on a public [[EN/documentation/basic_guide/scope_of_variables\|scope]]. You must avoid to have a marker of public [[EN/documentation/basic_guide/scope_of_variables\|scope]] with the same name as one of the modules of the library.	+	{{Caution\|The names of the Basic modules (by default Module1, Module2, etc) are known by Basic on a public [[EN/documentation/basic_guide/scope_of_variables\|scope]]. You must avoid to have a marker of public [[EN/documentation/basic_guide/scope_of_variables\|scope]] with the same name as one of the modules of the library.

	Example : Suppose that in your Basic library you have a module named PrintDoc. You must not declare, in any module of your library, a Public variable or a Public constant, or a Sub, or a Function, named PrintDoc.		Example : Suppose that in your Basic library you have a module named PrintDoc. You must not declare, in any module of your library, a Public variable or a Public constant, or a Sub, or a Function, named PrintDoc.

@@ Line 21: / Line 21: @@
   (Expression7 * Expression8)
-{{Documentation/Note|The underscore must always be the last character in a linked line and cannot be followed by a space or a tab or a comment, otherwise the code generates an error.
+{{Note|The underscore must always be the last character in a linked line and cannot be followed by a space or a tab or a comment, otherwise the code generates an error.
 }}
@@ Line 78: / Line 78: @@
 If you do have such collision, Basic may produce strange runtime error messages, or your Sub may not work.}}
-{{Documentation/VBAnote|The rules for constructing markers are different in {{OOo}} Basic than in VBA. For example, {{OOo}} Basic only allows special characters in markers when using <tt>Option Compatible</tt>, since they can cause problems in international projects.}}
+{{VBAnote|The rules for constructing markers are different in {{OOo}} Basic than in VBA. For example, {{OOo}} Basic only allows special characters in markers when using <tt>Option Compatible</tt>, since they can cause problems in international projects.}}
 Here are a few examples of correct and incorrect markers:

EN/documentation/basic guide/program overview - Revision history

Sancho at 10:47, 6 September 2011

Sancho at 07:49, 6 September 2011

Sancho: Created page with "{{DISPLAYTITLE:An Overview of an {{OOo}} Basic Program}}{{BreadCrumbL10n}} {{Documentat..."

Sancho: Created page with "
{{DISPLAYTITLE:An Overview of an {{OOo}} Basic Program}}
{{BreadCrumbL10n}} {{Documentat..."