Mobile development Four languages Overview two: Identifiers

Defined:

An identifier is a constant, a variable, a statement label, and the name of a user-defined function, as well as a later interface name, class name.

The C language stipulates that identifiers can only consist of letters, numbers, underscores, and can only begin with letters, underscores, and cannot be used as identifiers by keywords.

C + + is the same as the C language for identifiers.

Objective-c also ditto.

Java can use the $ symbol at the beginning and anywhere, with the rest above.

Conventions for Java identifiers:

1. Classes and interfaces usually use nouns and capitalize the first letter of each word.

2, the method name usually uses the verb, the first letter lowercase.

3, the constant is usually all uppercase, the words are separated by the underline.

4, the variable usually uses verbs, the first letter lowercase.

C # variables can be in the form of the "@" + keyword, with the rest in the C language.

For example: Char @new

second, the key words

Some identifiers that are assigned to a particular meaning are called keywords (or reserved words).

C's Keywords:

A total of 32 reserved words are defined by the ANSI standard:

1, program Control 12:

If,while, Break,else,switch,case,return,continue,goto,default,do,for

2, Data type 12:

Double,int,struct, Long,enum,char,float,short,union,unsigned,signed,void

3, Storage Category 4:

Auto, register, extern, static

4, the other 4:

Typedef,const,sizeof,volatile

C + + keywords:

A total of 74 keywords, fully inherited from the C language of the 32. The remaining 42 are as follows:

1, operator 11:

And, And_eq, Bitand, Bitor, compl, not, not_eq, or, Or_eq, XOR, Xor_eq

2, the other 15:

ASM, Delete,explicit,export,friend,inline,mutable,namespace,new,operator,this,typeid,typename,

Using,virtual,

3, data type 6:

bool,class,false,template,true,wchar_t,

4, type conversion 4:

Const_cast,dynamic_cast,reinterpret_cast,static_cast

5, Access rights control 3:

Private,protected,public

6, exception handling 3:

Try,catch,throw

objective-c Keyword:

A total of 58 keywords, fully inherited the C language keyword. The rest is as follows:

1, special predefined identifiers 15:

_cmd,__func__,bool,class,id,imp,nil,nil,no,nsobject,protocol,sel,self,super,yes

2, the other 11:

Restrict,out,oneway,inout,inline,in,byref,bycopy,_imaginary,_complex,_bool

java Keywords:

Java a total of 47 keywords.

The C language of 32 keywords Java inherits only 21, and does not inherit the following:

Goto, struct, union, signed, unsigned, auto, register, extern, typedef, const, sizeof

Your own 26 keywords are as follows:

1, Data type 5:

Boolean, Byte, class, interface, package

2, exception handling 5:

Try,catch,throw, throws, finally

3, Access rights control 3:

Private,protected,public

4, the other 13:

Abstract, extends, final, implements, import, instanceof, native, new, super, synchronized, this, transient, strictfp

C # Keywords:

C # A total of 79 keywords (2012 edition).

Abstract	As	Base	bool
Break	Byte	Case	Catch
Char	Checked	Class	Const
Continue	Decimal	Default	delegate-Delegation
Todo	Double	Else	Enum
Event	Explicit	extern	False
Finally	Fixed	Float	For
Foreach	Goto	If	Implicit
In	In (generic modifier)	Int	Interface
Internal	For	Lock	Long
Namespace	New	Null	Object
operator	Out	Out (generic modifier)	Override
Params	Private	Protected	Public
ReadOnly	Ref	Return	SByte
Sealed	Short	sizeof	Stackalloc
Static	String	struct	Switch
This	Throw	True	Try
typeof	UInt	ULong	Unchecked
Unsafe	UShort	Using	Virtual
void	Volatile	While

With the knowledge of these keywords, there is no error in naming identifiers yourself. More importantly, the identifiers from each language can also pry out some of the inner details of the language.

In the process of summing up these knowledge also let me learn a lot, language is the basis of all, lay the foundation in the programming practice will not be lost.

About the grammatical knowledge of the language, let me slowly.