Keywords Compared in Different Languages

Article
10/12/2006

This topic lists common programming tasks that can be summarized with a language keyword. For more information about tasks that need code examples, see Programming Concepts Compared in Different Languages with Code Examples.

Purpose	Visual Basic	Visual J#	C++	C# ^NEW	JScript	Visual FoxPro
Declare a variable	Private, Public, Friend, Protected, Static¹, Shared, Dim	public, private, protected static, final, volatile, transient	declarators (concept, not keyword)	declarators (keywords include user-defined types and built-in types)	var	[implicit declaration]; also PUBLIC, LOCAL, PRIVATE
Declare a named constant	Const	final	const	const readonly	const ^NEW	#DEFINE
Create a new object	New	new	new	new	new	n/a
	CreateObject()	n/a	CoCreateInstance() (for COM objects)		new ActiveXObject()	CREATEOBJECT; NEWOBJECT
Assign an object to an object variable	=	=	=	=	=	=; also STORE
Function/method does not return a value	Sub²	void	void	void	void	Void (COM servers only)
Overload a function or method (Visual Basic: overload a procedure or method)	Overloads ^NEW	(No language keyword required for this purpose)	(No language keyword required for this purpose)	(No language keyword required for this purpose)	(No language keyword required for this purpose)	(No language keyword required for this purpose)
Refer to the current object	Me³	this	this	this	this	This; Thisform
Make a nonvirtual call to a virtual method of the current object	MyClass	n/a	`MyClass:Func1()`, where `MyClass` is a C++ class with a member function `Func1`.	n/a	n/a	n/a
Retrieve character from a string	GetChar Function ^NEW	""	(p + 10) or p[10] where p is a char	[]	str[10], where str is a string, charAt, substring, substr⁴	SUBSTR( )
Declare a compound data type (Visual Basic: Structure)	Structure <members> End Structure	class, interface	class, struct, union __interface	struct, class, interface	class, interface ^NEW	n/a
Initialize an object (constructors)	Sub New()⁵	Constructors (concept, not keyword)	constructors (concept, not keyword)	Constructors, or system default type constructors	constructor (concept not keyword) ⁶	Init event
Terminate an object directly	n/a	n/a	~ClassName	n/a	n/a	n/a
Method called by the system just before garbage collection reclaims an object⁷	Finalize ^NEW (In Visual Basic 6.0, Class_Terminate)	finally	destructor	destructor	n/a	Destroy event
Initialize a variable where it is declared	Dim x As Long = 5 Dim c As New Car(FuelTypeEnum.Gas)	int x = 5; //or initialized by constructor C c(10);	int x=5;	// initialize to a value: int x = 123; // or use default constructor: int x = new int();	var x = 5 var y : car = new car()	n/a
Take the address of a function	AddressOf (For class members, this operator returns a reference to a function in the form of a delegate instance)	delegate, multicast, `/** @delgate */`	__delegate	delegate	Use the name of the function without parentheses	n/a
Callback	n/a	Pass the address of one function to another that calls the invoker back. For an example, see Using Callback Functions.	CALLBACK (a standard type); callback (IDL attribute)	n/a	n/a	n/a
Declare that an object can be modified asynchronously	n/a	volatile	volatile	volatile	n/a	n/a
Force explicit declaration of variables	Option Explicit	n/a. All variables must be declared prior to use.	n/a. All variables must be declared prior to use.	n/a. (All variables must be declared prior to use)	fast mode (on by default)	_VFP.LanguageOptions ^NEW
Test for an object variable that does not refer to an object	obj = Nothing	pObj == null	pobj == NULL	obj == null	obj == undefined obj == null	EMPTY(); ISNULL()
Value of an object variable that does not refer to an object	Nothing	null	n/a	null	null undefined	n/a
Test for a database null expression	IsDbNull	Supported by various data types in the System.Data.SqlTypes namespace	n/a	n/a	x == null	ISNULL( )
Test whether a Variant variable has been initialized	n/a	n/a	n/a	n/a	x == undefined	EMPTY( )
Define a default property	Default ^NEW	""	n/a	by using indexers	n/a	n/a

Object-Oriented Programming

Purpose	Visual Basic	Visual J#	C++	C# ^NEW	JScript	Visual FoxPro
Refer to a base class	MyBase ^NEW	super	__super	base	super ^NEW	BaseClass property; ParentClass property; DODEFAULT()
Declare an interface	Interface ^NEW	interface	__interface	interface	interface ^NEW	DEFINE CLASS
Specify an interface to be implemented	Implements (statement)	implements (clause on class declaration)	(Just derive from the interface) class C1 : public I1	class C1 : I1	implements ^NEW	IMPLEMENTS ^NEW
Declare a class	Class ^NEW <implementation>	class	class	class	class ^NEW	DEFINE CLASS MyClass AS <BaseClass>
Specify that a class can only be inherited. An instance of the class cannot be created.	MustInherit ^NEW	abstract	__abstract⁸ (Only in Managed Extensions for C++)	abstract	abstract ^NEW	n/a
Specify that a class cannot be inherited	NotInheritable ^NEW	final	__sealed (Only in Managed Extensions for C++)	sealed	final ^NEW	n/a
Declare an enumerated type	Enum <members> End Enum	n/a	enum	enum	enum ^NEW	n/a
Declare a class constant	Const	static final (Applied to a field declaration)	const	const (Applied to a field declaration)	const ^NEW	#DEFINE
Derive a class from a base class	Inherits C2 ^NEW	class C1 extends C2	Class C1 : public Base (No language keyword needed for this purpose)	class C1 : C2	class c1 extends c2 ^NEW	DEFINE CLASS MyClass AS ParentClass
Override a method	Overrides ^NEW	(No language keyword required for this purpose)	(No language keyword required for this purpose)	override	(No language keyword required for this purpose)	(No language keyword required for this purpose)
Declare a method that must be implemented in a deriving class	MustOverride ^NEW	abstract	Put = 0 at the end of the declaration (pure virtual method)	abstract	abstract ^NEW	(No language keyword required for this purpose)
Declare a method that can't be overridden	NotOverridable ^NEW (Methods are not overridable by default.)	final	__sealed (Only in Managed Extensions for C++)	sealed	final ^NEW	n/a
Declare a virtual method, property (Visual Basic), or property accessor (C#, C++)	Overridable	(Methods are virtual by default)	virtual	virtual	(Methods are virtual by default)	n/a
Hide a base class member in a derived class	Shadowing	n/a	n/a	n/a	new Modifier	n/a
Declare a typesafe reference to a class method	Delegate ^NEW	delegate, multicast, `/** @delgate */`	__delegate (Only in Managed Extensions for C++)	delegate	Use the name of the function without parentheses	n/a
Specify that a variable can contain an object whose events you wish to handle	WithEvents	n/a	n/a	(Write code - no specific keyword)	(Write code - no specific keyword)	EVENTHANDLER( ) ^NEW
Specify the events for which an event procedure will be called	Handles ^NEW (Event procedures can still be associated with a WithEvents variable by naming pattern.)	n/a	n/a	n/a	n/a	n/a
Evaluate an object expression once, in order to access multiple members	With objExpr <.member> <.member> End With	n/a	n/a	n/a	with⁹	WITH ... ENDWITH

Exception Handling

Purpose	Visual Basic	Visual J#	C++	C# ^NEW	JScript	Visual FoxPro
Structured exception handling	Try ^NEW <attempt> Catch <handle errors> Finally <always execute> End Try	try, catch, finally, throw	__try, __except, __finally	try, catch, finally, throw	try, catch, finally, throw	ONERROR( ), COMRETURNERROR( ), ERROR(); MESSAGE(), AERROR()
C++ exception handling	n/a	n/a	try, catch, throw	n/a	n/a	n/a

Decision Structures

Purpose	Visual Basic	Visual J#	C++	C# ^NEW	JScript	Visual FoxPro
Decision structure (selection)	Select Case ..., Case, Case Else, End Select	switch, case, break, default	switch, case, default, goto, break	switch, case, default, goto, break	switch, case, break	CASE
Decision structure (if ... then)	If ... Then, ElseIf ... Then, Else, End If	if, else	if, else	if, else	if, else	IF ... ENDIF
Loop structure (conditional)	While, Do [While, Until] ..., Loop [While, Until]	do, while, continue	do, while, continue	do, while, continue	do, while, break, continue	DO, WHILE (clauses)
Loop structure (iteration)	For ..., [Exit For,] Next For Each ..., [Exit For,] Next	for, break	for	for, foreach	for (x=0;x<10;x++){...} for (prop in obj) { print (obj[prop]);}	FOR (clauses), FOR ... ENDFOR, Continue, Next

Arrays

Purpose	Visual Basic	Visual J#	C++	C# ^NEW	JScript	Visual FoxPro
Declare an array	Dim a() As Long	int[] x = new int[5];	int x[5];	int[] x = new int[5];	var x : int[], var arr = Array()	DIMENSION, DECLARE
Initialize an array	Dim a() As Long = {3, 4, 5}	int[] x = {1,2,3,4,5};	int x[5]= {1,2,3,4,5};	int[] x = new int[5] {1, 2, 3, 4, 5};	var x : int[] = [1, 2, 3, 4, 5], var arr = new Array(1, 2, 3, 4, 5)]	DIMENSION, DECLARE
Reallocate array	Redim	n/a	n/a	n/a	arr.length=newSize(only for JScript arrays)¹⁰	DIMENSION, DECLARE

Class Scope

Purpose	Visual Basic	Visual J#	C++	C# ^NEW	JScript	Visual FoxPro
Visible outside the project or assembly	Public	public	public	public	public ^NEW	PUBLIC
Invisible outside the assembly (C#/Visual Basic) or within the package (Visual J#, JScript)	Friend	(Omitting the scope keyword specifies "package scope")	private	internal	internal ^NEW	n/a
Visible only within the project (for nested classes, within the enclosing class)	Private	private	private	private	private ^NEW	HIDDEN

Member Scope

Purpose	Visual Basic	Visual J#	C++	C# ^NEW	JScript	Visual FoxPro
Accessible outside class and project (Visual J#/JScript/C++/Visual Basic) or module (Visual Basic)	Public	public	public	public	public ^NEW	PUBLIC
Accessible outside the class, but within the project (C#, Visual Basic, C++) or package (Visual J#, JScript)	Friend	(Omitting the scope keyword specifies "package scope")	public private:	internal	internal ^NEW	n/a
Only accessible within class (Visual J#/JScript/C++/Visual Basic) or module (Visual Basic)	Private	private	private	private	private ^NEW	HIDDEN
Only accessible to current and derived classes	Protected ^NEW	protected	protected	protected	protected ^NEW	PROTECTED
Specify that a function or another class has access to private members of the declaring class	n/a	n/a	friend (Not allowed in the Managed Extensions for C++)	n/a	n/a	n/a
Protected inside the assembly and private to other assemblies	n/a	n/a	protected private: (Only in Managed Extensions for C++)	n/a	n/a	n/a

Misc. Lifetime

Purpose	Visual Basic	Visual J#	C++	C# ^NEW	JScript	Visual FoxPro
Preserve procedure's local variables	Static¹¹	static	static	n/a	n/a	PRIVATE
Shared by all instances of a class	Shared ^NEW	static	static	static	static ^NEW	n/a

Misc.

Purpose	Visual Basic	Visual J#	C++	C# ^NEW	JScript	Visual FoxPro
Comment code	' Rem	// /** / / */	//, /* */ for multiline comments	//, /* */ for multiline comments /// for XML comments	//, /* */ for multiline comments	*; &&
Case-sensitive?	No	Yes	Yes	Yes	Yes	No
Call Windows API	Declare <API>	Use J/Direct or Platform Invoke	n/a	use Platform Invoke	n/a	DECLARE - DLL
Declare and raise an event	Event, RaiseEvent	Use the java.awt.Event class or `/** @event */`	n/a	event	n/a	n/a
Threading primitives	SyncLock	synchronized		lock	n/a	n/a
Go to	Goto	n/a	goto	goto	n/a	n/a

1. The only place where Static can be used by itself to declare a variable — for example, Static x As Long — is within a procedure.

2. In Visual Basic, procedures declared with the Sub keyword cannot return values. If a procedure is to return a value, you must declare it with the Function keyword.

3. Me is not resolved at compile time, so you can use it as the return value of a property or method.

4. The substr function is still supported, but is no longer the preferred way to access characters within a string. The most efficient way to access a character from a particular location in a string is using brackets. For example, to access the tenth character in the string str, use str[10].

5. In Visual Basic, constructors for classes derived from .NET Framework System.Object are always named New.

6. Overloading is not allowed on constructors in JScript.

7. Typically, code in this method frees system resources that would not automatically be freed by the garbage collector.

8. In C++ an abstract class includes at least one pure virtual member.

9. Note there is no leading period such as you would use in Visual Basic. This feature can easily cause confusion, because variables may be mistaken for properties, and vice versa. Also note that the with statement produces slow code.

10. Does not reallocate the array, and does not "grow" it either. JScript arrays (declared as type Array) are always sparse and dynamic. Native arrays (declared as System.Array or as type[]) are not dynamic.

11. Static local variables of nonshared class methods are stored per class instance in Visual Basic rather than sharing a single copy, as in other languages. When Static is used to declare a variable, the value of that variable is preserved even if the variable looses and then regains scope.

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