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, countingetc.).
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