Reserved words

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

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
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
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:

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
abstract an abstract class cannot be instantiated, only inherited
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
forward Allow a subroutine to be used before it is declared
generic class creation modifier
local A function/procedure modifier only usable with Linux (for Kylix compatibility)
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
safecall subroutine calling convention
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