Reserved words

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The keywords of the individual compiler modes are summarized as follows:

• Turbo Pascal mode: the Turbo Pascal keywords are available for you to use
• Delphi mode: the Turbo Pascal and Object Pascal keywords are available for you to use
• Extended Free Pascal mode: the Turbo Pascal and Object Pascal keywords are available for you to use

Keywords are reserved words, ie they cannot be defined as identifiers by the programmer. This means that you cannot use these words to name your variables, constants, function and procedure names, class names, etc. In Pascal, in the source code, keywords are often shown in bold.

Reserved words in Turbo Pascal

The following keywords occur in Turbo Pascal mode:

Keyword	Description
and	Boolean operator requiring both conditions are true for the result to be true
array	multiple elements with the same name
asm	start of code written in assembly language
begin	start of a block of code
break	exit a loop
case	select a particular segement of code to execute based on a value
const	declare an identifier with a fixed value, or a variable with an initialized value
constructor	routine used to create an object
continue	skips an iteration in a loop and restart execution at the beginning of the loop
destructor	routine used to deallocate an object
div	integer divide operator
do	used to indicate start of a loop
downto	used in a for loop to indicate the index variable is decremented
else	used in if statement to provide an execution path when the if test fails
end	end of a block of code, a record or certain other constructs
false	boolean value indicating a test failed; opposite of true. As of FPC 3.0.0. False is no longer a keyword.
file	external data structure, typically stored on disc
for	loop used to increment or decrement a control variable
function	define start of a routine that returns a result value
goto	used to exit a segment of code and jump to another point
if	test a condition and perform a set of instructions based on the result
implementation	define the internal routines in unit
in	identifies elements in a collection
inline	machine code inserted directly into a routine
interface	public declarations of routines in a unit
label	defines the target jump point for a goto
mod	operator used to return the remainder of an integer division
nil	pointer value indicating the pointer does not contain a value
not	boolean operator that negates the result of a test
object	defines an object construct
of	defines the characteristics of a variable
on	defines an exception handling statement in the Except part of a Try statement
operator	defines a routine used to implement an operator
or	boolean operator which allows either of two choices to be used
packed	indicates the elements of an array are to use less space (this keyword is primarily for compatibility with older programs as packing of array elements is generally automatic)
procedure	define start of a routine that does not return a result value
program	defines start of an application. This keyword is usually optional.
record	group a series of variables under a single name
repeat	loop through a section of code through an until statement as long as the result of the test is true
set	group a collection
shl	operator to shift a value to the left; equivalent to multiplying by a power of 2
shr	operator to shift a value to the right; equivalent to dividing by a power of 2
string	declares a variable that contains multiple characters
then	indicates start of code in an if test
to	indicates a for variable is to be incremented
true	boolean value indicating a test succeeded; opposite of False. As of FPC 3.0.0. True is no longer a keyword.
type	declares kinds of records or new classes of variables
unit	separately compiled module
until	indicates end test of a repeat statement
uses	names units this program or unit refers to
var	declare variables
while	test a value and if true, loop through a section of code
with	reference the internal variables within a record without having to refer to the record itself
xor	boolean operator used to invert and or test

Reserved words in Object Pascal

Object Pascal extends the (Turbo) Pascal language with both support for dealing more easily with objects (object orientation) as well as other newer/more advanced concepts (threads, etc).

In addition to the reserved words in Turbo Pascal, the following reserved words are available in Delphi mode as well:

Keyword	Description
as
class
constref
dispose
except
exit
exports	exports symbols which will be publicly available
finalization	introduces an optional 'finalization' part of a unit.
finally	part of a try - finally - end block
inherited	calls function/procedure from ancestor class
initialization	introduces an optional 'initialization' part of a unit.
is	can be used as an operator or a modifier
library	used in a shared library unit instead of the reserved word unit
new
on
out
property
raise	causes an exception
self	reference to an instance of a class
threadvar	declare global variable to be thread local
try	part of Try .. Finally or Try .. Exception block

Reserved words in Extended Free Pascal

The reserved words in Extended Free Pascal mode include:

• Turbo Pascal mode reserved words
• Object Pascal mode reserved words
  

Modifiers (directives)

Modifiers are not strictly reserved words; however they are used in the same way as reserved words.

See the Free Pascal Reference Guide for details.

Modifiers	Description
absolute
abstract	an abstract class cannot be instantiated, only inherited
alias
assembler	pure assembler routine: routine is defined by asm … end
cdecl	C declaration modifier
Cppdecl	C++ declaration modifier
default	For indexed properties to use them without specifying the property name
export
external
forward	Allow a subroutine to be used before it is declared
generic	class creation modifier
index
local	A function/procedure modifier only usable with Linux (for Kylix compatibility)
name
nostackframe	compiler hint: omit stack frame if possible
oldfpccall	deprecated subroutine calling convention
override	overriding of virtual functions
pascal	use classic pascal calling convention
private	private accessibility modifier, only class members can access data/functions/procedures
protected	protected accessibility modifier, accessibility modifier, class members and inherited classes can access data/functions/procedures
public	public accessibility modifier, public access to data/functions/procedures
published	accessibility modifier, published properties are visible in IDE ar can be written to .lfm
read	property read access
register	define routine’s calling convention: pass first n parameters via GPRs
reintroduce
safecall	subroutine calling convention
softfloat
specialize	specialization of generic classes
stdcall	subroutine calling convention
virtual	describes a virtual method in OO programming
write	property write access

Unsupported Turbo Pascal modifiers

  Note: These modifiers are supported in the DOS cross compiler present in the FPC development version

The reason why these modifiers are not supported is that these modifiers deal with 16 bit code for DOS. In other words, these modifiers have special meaning for 16 bit programming under DOS and Windows 3.x.

As Free Pascal does not support 16 bit code (only 32 and 64 bit), these modifiers are irrelevant in Free Pascal code.

far	access addresses outside of the current 64KB segment
near	access addresses in the current 64KB segment

More functionality

Apart from the language features provided by the reserved words/keywords mentioned above, there is a lot of functionality available for the programmer in the various libraries:

• RTL: Run-Time Library, available for all FPC and Lazarus programs
• FCL: Free Component Library: a core set of libraries available for Lazarus programs and usually for FPC (FPC can be compiled without it, but that only happens on purpose for low-memory embedded systems etc)
• FPC Packages: other packages provided by FPC
• Lazarus components: these are Lazarus components that can be dropped on a form and often based on FCL or FPC packages
• Lazarus utility functions: e.g. the fileutil unit.

Apart from the libraries provided by FPC and Lazarus, there are more libraries/components available:

• FPC user-supplied units: see the FPC wiki
• Lazarus CCR: components
• User-supplied code on the internet: see open source repositories like SourceForge and GitHub.

See also

• Pascal basics