{"id":33,"date":"2018-07-09T11:08:11","date_gmt":"2018-07-09T11:08:11","guid":{"rendered":"http:\/\/itp1.epgpbooks.inflibnet.ac.in\/?post_type=chapter&p=33"},"modified":"2019-05-14T11:05:41","modified_gmt":"2019-05-14T11:05:41","slug":"overview-of-c","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/itp1\/chapter\/overview-of-c\/","title":{"rendered":"Overview of C++"},"content":{"raw":"
\"epgp<\/a>\r\n<\/span><\/div>\r\n\r\n
\r\n\r\n \r\n

Every Programming language like any language has basic character set on which the entire language is built. Language C++ has character set same as that of C.<\/p>\r\n \r\n\r\nCharacter sets<\/strong>\r\n\r\n \r\n

The basic source character set<\/em> consists of 96 characters: the space character, the control characters representing horizontal tab, vertical tab, form feed, and new-line, plus the following 91 graphical characters:14<\/p>\r\n \r\n\r\na b c d e f g h i j k l m n o p q r s t u v w x y z\r\n\r\n \r\n\r\nA B C D E F G H I J K L M N O P Q R S T U V W X Y Z\r\n\r\n \r\n\r\n0 1 2 3 4 5 6 7 8 9\r\n\r\n_ { } [ ] # ( ) < > % : ; . ? * + - \/ ^ & | \u223c ! = , \\ \" \u2019\r\n\r\n \r\n\r\nTrigraph Sequences<\/strong>\r\n\r\n \r\n

Some characters from the C and C++ character set are not available in all environments. We can enter these characters into a C or C++ source program using a sequence of three characters called a trigraph<\/em><\/strong>. The trigraph sequences are:<\/p>\r\n \r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
??=<\/td>\r\n#<\/td>\r\npound sign<\/td>\r\n<\/tr>\r\n
??(<\/td>\r\n[<\/td>\r\nleft bracket<\/td>\r\n<\/tr>\r\n
??)<\/td>\r\n]<\/td>\r\nright bracket<\/td>\r\n<\/tr>\r\n
??<<\/td>\r\n{<\/td>\r\nleft brace<\/td>\r\n<\/tr>\r\n
??><\/td>\r\n}<\/td>\r\nright brace<\/td>\r\n<\/tr>\r\n
??\/<\/td>\r\n\\<\/td>\r\nbackslash<\/td>\r\n<\/tr>\r\n
??\u2019<\/td>\r\n^<\/td>\r\ncaret<\/td>\r\n<\/tr>\r\n
??!<\/td>\r\n|<\/td>\r\nvertical bar<\/td>\r\n<\/tr>\r\n
??-<\/td>\r\n~<\/td>\r\ntilde<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n \r\n\r\nThe preprocessor replaces trigraph sequences with the corresponding single-character representation.\r\n\r\n<\/div>\r\n
\r\n\r\n \r\n\r\nEscape Sequences<\/strong>\r\n\r\n \r\n

Nonprintable characters also known as execution characters can be represented by an escape<\/em><\/strong> sequence<\/em>. <\/strong>Escape sequences are primarily used to put nonprintable characters in character and string literals. For example, you can use escape sequences to put such characters as tab, carriage return, and backspace into an output stream.<\/p>\r\n \r\n\r\nThe escape sequences and the characters they represent are:\r\n\r\n<\/div>\r\n\"\"\r\n

\r\n

Note: <\/strong>The line continuation sequence (\\ followed by a new-line character) is not an escape sequence. It is used in character strings to indicate that the current line continues on the next line. We can use escape sequences only in character constants or in string literals. An error message is issued if an escape sequence is not recognized. In string and character sequences, when you want the backslash to represent itself (rather than the beginning of an escape sequence), you must use a \\\\ backslash escape sequence. For example:<\/p>\r\n \r\n\r\ncout << \"The escape sequence \\\\n.\" << endl;\r\n\r\nThis statement results in the following output:\r\n\r\nThe escape sequence \\n.\r\n\r\n \r\n\r\nAlternative representations of operators and punctuators<\/strong>\r\n\r\n \r\n

In addition to the reserved language keywords, the following alternative representations of operators and punctuators are also reserved in C and C++:<\/p>\r\n \r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Alternative<\/strong><\/td>\r\nOperator<\/strong><\/td>\r\nAlternative<\/strong><\/td>\r\nOperator<\/strong><\/td>\r\nAlternative<\/strong><\/td>\r\nOperator<\/strong><\/td>\r\n<\/tr>\r\n
Representation<\/strong><\/td>\r\n\/Punctuation<\/strong><\/td>\r\nRepresentation<\/strong><\/td>\r\n\/Punctuation<\/strong><\/td>\r\nRepresentation<\/strong><\/td>\r\n\/Punctuation<\/strong><\/td>\r\n<\/tr>\r\n
<\/td>\r\nRepresented<\/strong><\/td>\r\n<\/td>\r\nRepresented<\/strong><\/td>\r\n<\/td>\r\nRepresented<\/strong><\/td>\r\n<\/tr>\r\n
<%<\/strong><\/td>\r\n{<\/td>\r\nand<\/td>\r\n&&<\/td>\r\nand_eq<\/td>\r\n&=<\/td>\r\n<\/tr>\r\n
%><\/strong><\/td>\r\n}<\/td>\r\nbitor<\/td>\r\n|<\/td>\r\nor_eq<\/td>\r\n|=<\/td>\r\n<\/tr>\r\n
<:<\/strong><\/td>\r\n[<\/td>\r\nor<\/td>\r\n||<\/td>\r\nxor_eq<\/td>\r\n^=<\/td>\r\n<\/tr>\r\n
:><\/strong><\/td>\r\n]<\/td>\r\nxor<\/td>\r\n^<\/td>\r\nnot<\/td>\r\n!<\/td>\r\n<\/tr>\r\n
%:<\/strong><\/td>\r\n#<\/td>\r\ncompl<\/td>\r\n~<\/td>\r\nnot_eq<\/td>\r\n!=<\/td>\r\n<\/tr>\r\n
%:%:<\/strong><\/td>\r\n##<\/td>\r\nbitand<\/td>\r\n&<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n
\r\n\r\n \r\n\r\nWide Characters<\/strong>\r\n\r\n \r\n

The C <\/a>and C++ <\/a>standard libraries include a number of facilities <\/a>for dealing with wide characters and strings composed of them. The wide characters are defined using datatype wchar_t, which in the original C90 standard was defined as<\/p>\r\n \r\n

\"an integral type whose range of values can represent distinct codes for all members of the largest extended character set specified among the supported locales\" (ISO 9899:1990 \u00a74.1.5)<\/p>\r\n \r\n

Both C and C++ <\/a>introduced fixed-size character types char16_t and char32_t in the 2011 revisions of their respective standards to provide unambiguous representation of 16-bit and 32-bit Unicode transformation formats, leaving wchar_t implementation-defined. The ISO\/IEC 10646:2003 Unicode standard 4.0 says that:\u00a0 \"The width of wchar_t is compiler-specific and can be as small as 8 bits. Consequently, programs that need to be portable across any C or C++ compiler should not use wchar_t for storing Unicode text. The wchar_t type is intended for storing compiler-defined wide characters, which may be Unicode characters in some compilers.\"<\/p>\r\n \r\n\r\nIdentifiers<\/strong>\r\n\r\n \r\n

An identifier<\/em> is the user-defined name of a program element. In C++ identifier provides names for the following language elements:<\/p>\r\n \r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Functions\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Objects\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Labels\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Function parameters\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Macros and macro parameters\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Typedefs\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Enumerated types and enumerators\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 C++ Classes and class members\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 C++ Templates\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 C++ Template parameters\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 C++ Namespaces\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Struct and union names\r\n

An identifier starts with a letter A to Z or a to z or an underscore (_) followed by zero or more letters, underscores, and digits (0 to 9). In C++there is no limit on the length of the identifer , but implementers often impose one<\/p>\r\n\r\n<\/div>\r\n

\r\n\r\nKeywords<\/strong>\r\n\r\n \r\n

Keywords <\/em>are identifiers reserved by the language for special use. Following is the list of keywords common to both the C and C++.<\/p>\r\n\"\"\r\n

Only the exact spelling of keywords is reserved. For example, do is reserved but DO is not.<\/p>\r\n \r\n\r\nThe C++ language also reserves the following keywords:<\/strong>\r\n\r\n\"\"\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 We will see their use in successive modules<\/span>Data Types<\/strong>\r\n\r\n \r\n

Data type define the way you store the values used by and created by the program. Defining a data type means defining what constants (generally in terms of range) a variable of that data type can store and what operations can be performed on that value.<\/p>\r\n \r\n

Data type can be built in or abstract. A built in data type compiler intrinsically understand. It is predefined and known to the compiler. Therefore we don\u2019t need to define them , they are made available to us for use. As C++ is superset of C, most of the built in data types are inherited as is in C++, and they can be used as we use them in C. The basic scalar data type namely int, float and double along with their modifiers signed, unsigned, short and long can be used as we use them in C. Pointers in C++ also can be used the way we use them in C except few additions that we will discuss in next module.<\/p>\r\n \r\n\r\n<\/div>\r\n

\r\n\r\nFollowing is the complete list of fundamental data types in C++:\r\n\r\n\"\"\r\n\r\nNew Data types in C++<\/strong>\r\n\r\n \r\n

In addition to these built in data types inherited from C , another data type boolean was added to standard C++ . The keyword used for this data type is bool . The variables of bool data type can have two possible values \u2013 built in constants true (which converts to integer 1) and false ( which converts to integer 0 ).<\/p>\r\n \r\n\r\nExample :\r\n\r\n \r\n\r\nbool found;\r\n\r\n \r\n\r\nIt can be assigned two values\r\n\r\n \r\n\r\nfound = true;\r\n\r\nOr\r\n\r\n \r\n\r\nfound = false\r\n\r\n<\/div>\r\n

\r\n\r\n\"\"\r\n\r\nAbstract Data type<\/strong>\r\n\r\n \r\n

Also C++ allows us to create our own data type, which with careful crafting can be made to look and behave quite similar to standard data type. They are also denoted as Abstract Data type. We will discuss about abstract data type in detail in modules 5.<\/p>\r\n \r\n\r\nVariable Declaration in C++<\/strong>\r\n\r\n \r\n

C and C++ are block structured programming languages. Scope and lifetime of the variables are determined by the block in which it is defined. The only difference being, that in C variables can only be defined in the beginning of the block , whereas in C++ variables can be defined anywhere in the block with only one restriction that they should be defined before their first use. For example<\/p>\r\n \r\n\r\n#include <iostream>\r\n\r\nUsing namesapce std;\r\n\r\nvoid main(void)\r\n\r\n{\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
int value1 ;<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n
value1 = 10;<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n
\u2026\u2026\u2026\u2026\u2026\u2026.<\/td>\r\n\/\/\u00a0 some executable code here<\/td>\r\n<\/td>\r\n<\/tr>\r\n
\u2026\u2026\u2026\u2026\u2026\u2026.<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n
int value2;<\/td>\r\n\/\/\u00a0 this will not work in C but will work in C++<\/td>\r\n<\/td>\r\n<\/tr>\r\n
\u2026\u2026\u2026\u2026\u2026\u2026<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n
{<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n
int value 3;<\/td>\r\n\/\/\u00a0 this will work in C and C++ both<\/td>\r\n<\/td>\r\n<\/tr>\r\n
\u2026\u2026\u2026\u2026\u2026\u2026..<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n
\u2026\u2026\u2026\u2026\u2026..\u2026<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n
}<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n
}<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n
<\/td>\r\n<\/td>\r\n<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n
\r\n\r\nStorage Classes<\/strong>\r\n\r\n \r\n

Like C, C++ also has four storage classes namely auto, extern, register and static. Implementation of first three storage classes is similar to C. But static storage class has been extended in C++ for specific use with user defined data type. We will discuss this in detail in modules 6.<\/p>\r\n \r\n\r\nOperators in C++<\/strong>\r\n\r\n \r\n\r\nBeing superset of C, C++ has inherited all the operators from C. Apart from these operators, C++ has added new operators as well.\r\n\r\n \r\n\r\nHere we will discuss following commonly used operators.\r\n\r\n \r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Scope resolution\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 New\r\n\r\n\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 delete\r\n\r\n \r\n\r\nDiscussion of other operators will require knowledge of other C++ constructs. We will discuss them in later modules as appropriate.\r\n\r\n \r\n\r\nScope Resolution Operator ::<\/strong>\r\n\r\n \r\n\r\nWe know that in C & C++. We can define the variables of the same name in different scope. For example have a look at the following program.\r\n\r\n \r\n\r\nint value = 10;\r\n\r\n \r\n\r\nvoid main(void)\r\n\r\n{\r\n\r\nint value = 20;\r\n\r\n \r\n\r\ncout >> value;\r\n\r\n}\r\n\r\n \r\n

Which value will be displayed ?<\/p>\r\n

Yes you are right. The variable in the innermost scope will prevail and therefore 20 will be displayed. This is logical enough. But what if we want the global value to be displayed ? The answer to this is scope resolution operator ::<\/p>\r\n \r\n\r\nint value = 10;\r\n\r\n \r\n\r\nvoid main(void)\r\n\r\n{\r\n\r\nint value = 20;\r\n\r\n \r\n\r\ncout >> :: value;\r\n\r\n}\r\n\r\n \r\n\r\nHere 10 will be displayed.\r\n\r\n<\/div>\r\n

\r\n\r\n \r\n

The :: (scope resolution) operator is used to qualify hidden names so that you can still use them. You can use the unary scope operator if a namespace scope or global scope name is hidden by an explicit declaration of the same name in a block or class. For example:<\/p>\r\n \r\n\r\n \r\n\r\nint value = 0;\r\n\r\n \r\n\r\nvoid main(void)\r\n\r\n{\r\n\r\nint value = 0;\r\n\r\n \r\n\r\n::\u00a0\u00a0 value = 1; \/\/ set global count to 1\r\n\r\nvalue = 2; \/\/ set local count to\r\n\r\n2 return 0;\r\n\r\n \r\n\r\n}\r\n\r\n \r\n

The declaration of value declared in the main() function hides the integer named value declared in global namespace scope. The statement :: value = 1 accesses the variable named value declared in global namespace scope.<\/p>\r\n \r\n

You can also use the class scope operator to qualify class names or class member names. If a class member name is hidden, you can use it by qualifying it with its class name and the class scope operator. We will discuss this in later modules.<\/p>\r\n \r\n\r\nNew and Delete Operators<\/strong>\r\n\r\n \r\n

We have used malloc(), calloc() , realloc() and free() functions for program controlled dynamic memory allocation and deallocation . These functions can be used in C++ as well, but apart from these functions C++ also provides operators new and delete for same.<\/p>\r\n \r\n\r\nNew Operator<\/strong>\r\n\r\n \r\n\r\nThe syntax of new operator is as follows\r\n\r\n \r\n\r\n<data type>\u00a0 *ptr\u00a0\u00a0 = new <data type>\r\n\r\nFor example\r\n\r\nint *iptr = new int;\r\n

will allocate no of bytes needed to store integer and address of the allocated memory will be returned which we can store in a pointer to integer variable.<\/p>\r\nNew operator can be used to allocate memory to scalar data type as well as\u00a0float<\/span>\r\n\r\n<\/div>\r\n

\r\n\r\nfloat*fptr = new float ;\r\n\r\nchar*cptr = new char ;\r\n\r\n<\/div>\r\n
\r\n\r\nWe can initialize the allocated memory as follows\r\n\r\n \r\n\r\nint *iptr = new int(10);\r\n\r\nHere the memory allocated for integer will be initialized with value 10.\r\n\r\n<\/div>\r\nWe can also get memory allocated for array as follows\r\n\r\n \r\n\r\nint *array = new int [25];\r\n\r\nthis will allocate memory for 25 integers\r\n\r\nint\u00a0 *array = int[5][5];\r\n\r\n \r\n\r\nthis will allocate memory for 5 *5 two dimensional array.\r\n\r\n \r\n\r\nDelete operator<\/strong>\r\n\r\n \r\n\r\nDelete operator also has simple syntax\r\n\r\ndelete p;\r\n\r\nthis will release memory being ponted by pointer variable p.\r\n\r\n \r\n\r\nThe advantage of using new and delete operator over memory allocation function.<\/strong>\r\n\r\n \r\n\r\nUse of new and delete operator is much more efficient and simple as compared to memory allocation functions\r\n