Elements of C++ Language

Tokens

The smallest unit in the program is called a token. C++ has the following tokens:

C++ Character Set

Character set is a set of valid characters that a language can recognize. A character represents any letter , digit or any sign. The C++ has the following character set

Letters: A-Z, a-z

Digit: 0-9

Special symbol: Space + - * / ^ \ ( ) [ ] { } = != < > . ' " , $ ; : % ! & ? _ # <= >= @

White Spaces: Blank space, Horizontal tab , New line

Other: C++ can process any of the 256 characters as data or as literals.

Identifiers

Identifiers are very important in C++ and are used in all programs. What is an identifier?

In the previous program ‘check’ was declared as a character variable. The identifier in this case is ‘check’.

Basically identifiers are names that are given to variables, constants or functions.

In the previous program there are two identifiers: ‘check’ and ‘i’.

C++ permits the use of a huge variety of names for identifiers like:

test

Test

int_test

var1

var123

c_b_f

var

Almost any name you can think of can be used as an identifier but there are some restrictions. An identifier should not start with a number.

The first character of an identifier should be an alphabet or an underscore ( _ ).

). After the first character, numbers can be used in the identifier. Remember the following:

Never start an identifier with anything other than a letter or an underscore. It is better to use a letter than starting with underscores.

Do not use keywords as identifiers (ex: do not name an identifier as int). Uppercase and Lowercase identifiers are different (Check is different from check).

Be careful when using characters that look similar to each other. For example ‘1’ (the number one) and ‘l’ (the lowercase alphabet L) look alike.

Use names that are easy to understand (if you are storing the salary of a person, name the variable as ‘salary’ instead of declaring it as ‘x’.

Do not use very long names.

Do not name many variables with similar names (avoid using identifiers like: count, counter, counting etc.).

Keywords

Keywords are reserved words in C++ programming. They should not be used as identifiers and all keywords should be in lower case. The 63 keywords are tabulated below:

asm

Auto

bool

break

case

catch

char

class

Const

const_cast

continue

default

Delete

do

double

Dynamic_cast

else

enum

explicit

Export

extern

false

float

for

friend

goto

If

inline

int

Long

mutable

namespace

new

Operator

private

protected

Public

register

reinterpret_cast

return

Short

signed

sizeof

Static

static_cast

struct

switch

Template

this

throw

True

Try

typedef

typeid

typename

union

unsigned

Using

virtual

void

volatile

wchar_t

while