C++ Constant/Literals and Variable | Identifiers | My CS Tutorial

Cconstant and variables in c++ | My CS Tutorial

IDENTIFIER IN C++

Identifier refereds to the names of variables,functions,functions,arrays, classes etc created by programmer.
Each language has its own rules for naming these identifiers. The following rules are common to both C and C++ .

(i) Only alphabetic characters digits and underscore are permitted.
(ii) The name cannot start with a digit .
(iii) The uppercase letter and lowercase letter are distinict.
(iv) We declared keyword cannot be used as a variable name.
(v) The major difference between C and C++ identifier is the limit on the length of a name.
while C programming recognise first 32 character in the name, but c++ places no limit on its language.

CONSTANT/LITERALS

Constants refer to fixed values that the program may not alter and they are called literals.

Constants can be of any of the basic data types and can be divided into Integer Numerals,

Floating-Point Numerals, Characters, Strings and Boolean Values.

Integer Literals

An integer literal can be a decimal, octal, or hexadecimal constant. A prefix specifies the base

or radix: 0x or 0X for hexadecimal, 0 for octal, and nothing for decimal.

An integer literal can also have a suffix that is a combination of U and L, for unsigned and

long, respectively. The suffix can be uppercase or lowercase and can be in any order.

Here are some examples of integer literals:-

212 // Legal

215u // Legal

Floating-point Literals

A floating-point literal has an integer part, a decimal point, a fractional part, and an exponent

part. You can represent floating point literals either in decimal form or exponential form.

While representing using decimal form, you must include the decimal point, the exponent, or

both and while representing using exponential form, you must include the integer part, the

fractional part, or both. The signed exponent is introduced by e or E.

Here are some examples of floating-point literals:-

3.14159 // Legal

314159E-5L // Legal

Boolean Literals

There are two Boolean literals and they are part of standard C++ keywords:

(a) A value of true representing true.

(b) A value of false representing false.

You should not consider the value of true equal to 1 and value of false equal to 0.

Character Literals

Character literals are enclosed in single quotes. If the literal begins with L (uppercase only),

it is a wide character literal (e.g., L'x') and should be stored in wchar_t type of variable.

Otherwise, it is a narrow character literal (e.g., 'x') and can be stored in a simple variable of char type.

A character literal can be a plain character (e.g., 'x'), an escape sequence (e.g., '\t'), or a

universal character (e.g., '\u02C0').

There are certain characters in C++ when they are preceded by a backslash they will have special meaning and they are used to represent like newline (\n) or tab (\t). Here, you have a list of some of such escape sequence codes:-

Escape sequence Meaning

\\ \ character

\' ' character

\" " character

\? ? character

\a Alert or bell

\b Backspace

\f Form feed

\n Newline

\r Carriage return

\t Horizontal tab

\v Vertical tab

\ooo Octal number of one to three digits

\xhh . . . Hexadecimal number of one or more digits

String Literals

String literals are enclosed in double quotes. A string contains characters that are similar to

character literals: plain characters, escape sequences, and universal characters.

You can break a long line into multiple lines using string literals and separate them using whitespaces.

Here are some examples of string literals. All the three forms are identical strings.

Example:-

"hello, dear"

"hello, \

dear"

"hello, " "d" "ear"

VARIABLE IN C++

A variable provides us with named storage that our programs can manipulate. Each variable in C++ has a specific type, which determines the size and layout of the variable's memory;
the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

The name of a variable can be composed of letters, digits, and the underscore character. It must begin with either a letter or an underscore. Upper and lowercase letters are distinct because C++ is case-sensitive:-

Type Description

bool Stores either value true or false.

char Typically a single octet (one byte). This is an integer type.

int The most natural size of integer for the machine.

float A single-precision floating point value.

double A double-precision floating point value.

void Represents the absence of type.

wchar_t A wide character type.

C++ also allows to define various other types of variables, which we will cover in subsequent chapters like Enumeration, Pointer, Array, Reference, Data structures, and Classes.

VARIABLE DECLARATION IN C++

int i, j, k;

char c, ch;

float f, salary;

double d;

C++ Constants and variables | C++ Identifiers | Types of constants | Declaration of variable in c++ programming languages | int,float,double,boolean, character constant in c++ |My CS Tutorial

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