THE BASICS: C++ PROGRAMMING LANGUAGE

UNDERSTANDING A SIMPLE C++ PROGRAM

#include <iostream>

using namespace std;

int main() {

cout << "hello world" << endl;

return 0;

}

**This program above prints out "hello world" when it is compiled and executed.

Iostream - Input Output stream

Function: It declares a set of functions for the standard input output.  It also defines I/O of cin,cout.

Cout - A predefined object of Iostream class

Std - A namespace which is used to group data to prevent name conflicts with others with the same name.

Main() - A special function that is called when the program is compiled and run

Return 0; - Returns the 0 value to previous function 

Std::cout - used to call the cout object in the namespace standard

VARIABLES

Variables are quantities that may change within the context of a mathematical problem or experiment.  With this in mind, variables use single letter to represent it.  The letters x, y, z are common letters used to represent variables.

In other words, variable is any characteristics, number or quantity that can be measured or counted.  A variable may also be called a data item.  Age, business income and expenses, country of birth and class grades are examples of variables. 

WHAT ABOUT VARIABLES IN C++

In C++, variables are names given to memory locations.  The value stored in a location can be changed during execution.  In other words, its a container (storage area) to store data.  A variable is just a name given to a memory location.  All the operations done on the variable effects the memory location.  In C++, all the variables need to be declared before use.  Variables need to be given a unique name.

Example:  int distance = 20 ;

Here the distance is a variable with the data type int.  The value 20 assigned to this variable.

The value of the variable can be changed:

int distance = 20    //distance is 20

int distance = 5     // distance is 5

Rules for naming variables:

A variable can only have alphabets, numbers and underscore

A variable name can't begin with a number

A variable name cannot begin with upper case letter

A variable name cannot be a keyword - example: public, float, int...

There are 3 types of variables:

Local Variables

Instance Variable

Static Variable

LITERALS

Literals are use to represent fixed values.  This literals can be used directly in the code. Examples: 2. 3.8, 'c' and so on.

Here are a list of LITERALS:

Integer is a numeric literal.  There are three types of integer literals in C++:

decimal : 0, -8, 24

octal: 021, 077, 033...

hexadecimal: 0x7f, 0x2a,

**In C++, Octal starts with 0 and hexadecimal starts with 0x.

Floating literal has exponential form or fractional form.

examples:

-2.0

0.000024

-0.22E05

Character literal is gotten from a single character inside single quotation marks.

'd', 'F', '2', '{'

Escape Sequences 

Examples:

\b            backspace

\n            newline

\r             return

\v            vertical tab

\'              single quotation mark

\0             null character

String Literals

Examples:

"good"                        string constant

" "                                null string constant

"      "                            string constant of  white spaces

"C"                               string constant with single character

"What a day\n"            prints string with a new line

Constant

We can create values where the values can never change

example:

const int speed = 2800 ;

DATA TYPES

Data types are declaration for variables.  This determines the size and type of data for variables.

example:

int distance = 20 ;

The distance is a variable with data type int.  This means the variable can only store 2 bytes or 4 bytes only.

C++ BASIC I/O

In C++, cout sends out formatted output.  We use the cout object along with the << operator to display output.

INTEGERS

FLOATING POINT LITERALS

CHARACTERS

ESCAPE SEQUENCES

STRING LITERALS

CONSTANTS

DATA TYPES

BASIC I/O

TYPE CONVERSION

OPERATORS

COMMENTS