basic features of c

7/30/2019 Basic Features of c

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BASIC FEATURES OF C++


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Characters and character set

The characters used in the C++ program are

upper and lower case letters, A to Z and a to z

digits 0 to 9

the space character

control characters- new line, horizontal andvertical tab, form feed, bell

special characters (or symbols)

_ { } [ ] # ( ) < > $ : ; . ? * + -/ ^ & | ~ ! = , \ " '


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Variable

A variable is a name given to a memorylocation where you can store a data of a

particular type. The type is specified when thevariable is declared.

The name you can give to a variable canconsist of any combination of upper or lowercase letters, underscores ( _ ) and the digits (

0 to 9 ).


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A variable name is case sensitive. (C++ is acase sensitive language). This means length

and Length, LENGTH are different names.

A variable name cannot begin with a digit.

Examples of variable names:

monthly_salary, temperature, pay, mark,mark_ce204,


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Declaration of Variable

Examples of variable declaration:

int student_no;

int age;

int student_no, age;

string name;

double length, width, area;

int count=0;

int a=5, b=2;


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Basic data types

char

short

int

long

float

double

long double

string


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There are also type such as unsignedlong, unsigned short, unsigned intsigned long, signed short, signed int.

Typically float will provide 7 digitprecision, double will provide 15 digit

precision and long double will provide19 digit precision


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Keywords

These are reserved words that have particularsignificance and when needed are to be used

as it is. In the above program include,iostream, using, namespace, std, int, cout,return are keywords.


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blocks

A statement is analogous to a sentencein any language.

A C++ statement expresses a completeinstruction to the computer. Statementsare basic units for specifying what our

program is to do.

Most C++ statements end with a

semicolon.


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Examples of C++ statement andstatement block:

#include

double result; //declaration

double result=0.0; //declaration and initialization

length = 5.0; // assignment

if(marks>=40)

cout


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Whitespace

Whitespace refers to spaces, horizontal andvertical tabs and newline characters.Whitespaces are required in a C++ statement forthe compiler to be able to distinguish between the

elements of the statement.


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Function, function name and

function body

A function is a self-contained block of codereferenced by a name. There may be morethan one function in a C++ program, but there

shall be at least one function named mainandnot more than one function shall have thename main.

The brackets ( ) after the function name isessential. A function may have arguments thatare placed within these brackets.

The function has a type.


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directive

#include includes the contents of theheader file iostream into the program.

iostream is one of several standard header files thatare supplied with C++ compiler.

The header files contain information (code) for theavailable library functions. The name cout is defined inthe header file iostream. This is a standard header filethat provides the definitions necessary for standardinput and output facilities. The standard input device isthe keyboard and the standard output device is themonitor.


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Namespace

The namespace refers to a group of severalnames (or entities). The entities in the C++standard library are all defined within anamespace called std. You may also consider

namespace as a surname. You may consider thatthe full name ofcout is std::cout. If we omit theusing directive we can write the output statementas

std::cout


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Returnstatement The return statement ends the function and

returns control to the operating system. It alsoreturns a value (0 in the above example) to theoperating system.


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EXAMPLE

/* Program that finds the average

of two numbers */

#include

using namespace std;

int main()

{

double num1, num2, average;

cout

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