2.1 Basic elements in c++  (Page 2/6)

The header file for the iostream class is iostream.h.

The #include statement is one of the several preprocessor directives that are used with C++.

The preprocessor is a program that runs before the compiler. When it encounters an #include statement, the preprocessor places the entire contents of the designated file into the current file.

Preprocessor directives and include statements allow the current file to use any of the classes, functions, variables, and other code contained within the included file.

Example: To include the iostream.h file you use the following statement:

#include<iostream.h>

An i/o manipulator is a special function that can be used with an i/o statement. The endl i/o manipulator is part of the iostream classes and represents a new line character.

Example:

cout<<“Program type: console application”<<endl;

cout<<“Create with: Visual C++ “<<endl;

cout<<“Programmer: Don Gesselin”<<endl;

All statements in C++ must end with a semicolon. Large statements can span multiple lines of code.

Example:

cout<<“Program type: console application,”

<<“Create with: Visual C++ “

<<“Programmer: Don Gesselin”;

Comments

Comments are lines that you place in your code to contain various type of remarks. C++ support two types of comments: line and block.

C++ line comments are created by adding two slashes (//) before the text you want to use as a comment.

Block comments span multiple lines. Such comments begin with /* and end with the symbols */.

Example:

void main()

{

/*

This line is part of the block comment.

This line is also part of the block

comment.

*/

cout<<“Line comment 1 “;

cout<<“Line comment 2 “;

// This line comment takes up an entire line.

}

All programs should contain comments. They are

remarks, insights, wisdom in code without affecting the program. The compiler ignores comments

.

Data types and operators

Data types

A data type is the specific category of information that a variable contains.

There are three basic data types used in C++: integers, floating point numbers and characters.

Integers

An integer is a positive or negative number with no decimal places.

- 259 -13 0 200

Floating Point Numbers

A floating point number contains decimal places or is written using exponential notations.

-6.16 -4.4 2.7541 10.5

Exponential notation, or scientific notation is a way of writing a very large numbers or numbers with many decimal places using a shortened format.

2.0e11 means 2*1011

C++ supports three different kinds of floating-point numbers:

• float (i.e. single precision numbers),
• double (i.e. double precision numbers)
• long double.

A double precision floating-point number can contain up to 15 significant digits.

The Character Data Type

To store text, you use the character data type. To store one character in a variable, you use the char keyword and place the character in single quotation marks.

Example:

char cLetter = ‘A’;

Escape sequence

The combination of a backlash (\) and a special character is called an escape sequence. When this character is placed directly in front of a select group of character, it tells the compiler to escape from the way these characters would normally be interpreted.