WHAT IS C++ | Definition from ProLearner00

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INTRODUCTION /  What is C++

The C++ programming language was developed at AT&T Bell Laboratories in the early 1980s by Bjarne Stroustrup. He found 'C lacking for simulations and decided to extend the language by adding features from his favourite language, Simula 67. Simula 67 was one of the earliest object oriented languages. Bjarne Stroustroup called it "C with classes" originally. The name C++ (pronounced C plus plus) was coined by Rick Mascitti where "++" is the C increment operator. Ever since its birth, C++ evolved to cope with problems encountered by users, and through discussions at AT&T. However, the maturation of the C++ language is attested to by two recent events: (i) the formation of an ANSI (American National Standard Institute) C++ Committee and (ii) the publication of The Annotated C++ Reference Manual by Ellis and Stroustrup.
 

C++ CHARACTER SET
 
Character set is a set of valid characters that a language can recognise. A character represents any letter, digit, or any other sign.
 
The C++ has the following character set:
 
Letters       A-Z, a-z
 
Digits       0 -9
 
Special Symbols          Space  + -* /^ \ ( ) [ ] { } = ! =  < > . ‘ “ $ , ; : % ! & ? _(underscore) # <=
                                    >= @
 
White Spaces              Blank space, horizontal tab(      ), Carriage return (    ), Newline, form feed
 
Other Characters         C++ can process any of the 256 ASCII characters as data or as literals.
 
<> 5.; %! &? (underscore) # <= >= @ Blank space, Horizontal tab (→), Carriage return (-), Newline, Form feed. C++ can process any of the 256 ASCII characters as data or as literals. 

What is TOKENS??

Token The smallest individual unit to a program is known as a Token or a lexical unit.
 
TOKENS (LEXICAL UNITS)
In a passage of text, individual words and punctuation marks are called tokens o lexical units or lexical elements. C++ has the following tokens:
 
Keywords
Identifiers
Literals
Punctuators
Operators
 

 What is Keyword??

Keyword is a word Having special meaning reserved  by programming language.


Keywords are the words that convey a special meaning to the language compiler. These are reserved for special purpose and must not be used as normal identifier names.
 
The original keywords:
C++ (developed by Stroustrup) contains the following
 
 
Continue         float     new    signed              try                    auto
 
Default                        for       operator           sizeof               break               typedef
 
Delete              friend              private             static                union               case
 
Do                   goto                 protected         struct               unsigned          if
 
Public              switch              char                 virtual              inline               template
 
Enum               void                 int                    retur                 this                  extern
 
catch double                else                  register                        volatile                        class                 const
 
long                 short                throw               while
 
 
With revisions and additions, recent completed list of keywords also includes these keywords:
 
Using, namespace, bal, static, cast, const, cast, dynamic, cast, true ,false
 
In addition, identifiers containing a double underscore (___) are reserved for use by C++ implementations and standard libraries and should be avoided by users.
 

What is Identifier??

An identifier is an arbitrarily long sequence of letters and digits. The first character must be a letter; the underscore (_) counts as a letter. Upper and lower-case letters are different. All characters are significant.
 
Identifiers are fundamental building blocks of a program and are used as the general terminology for the names given to different parts of the program viz. variables, objects, classes, functions, arrays etc. Identifier forming rule of C++ has been specified in the adjacent box.
 
Even though original C++ considers all the characters, (in an identifier) significant yet it is implementation dependent. It varies from one version to another.
 
C++ is case sensitive as it treats upper and lower-case characters differently.
 
The following are some valid identifiers:
 
Myfile                   DATE9 7.77          MYFILE
CHK                        _DS                        721029  FILE13
The following are some invalid identifiers:
 
DATA-REC           contains special character (other than A-Z, 2 and )
29CLCT Starting with a digit                          break
reserved keyword                           contains special character dot (-)              My.file

Literals

Literals (often referred to as constants) are data items that never change their value during a program run.
 
C++ allows several kinds of literals:
bool literal
integer-constant
 
character-constant
 
floating-constant
 
Estring-literal

 

 

 

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