How Create a C++ Program

#include using namespace std; void main() { cout<<“Hello World”; } If your compiler gives error then

#include void main() { cout<<“Hello World”; cout<<endl; // for going to new line cout<<“ good bye”; } cout is an object for printing out some thing on the screen.

#include void main() { cout<<“Hello World \n”; cout<<“ good bye”; } we can use \n instead of cout<<endl;

How to run your program Using Linux or unix: g++ myFile.cpp./a.out g++ myFile.cpp myFile.out./myFile.out

Declare Statement & Variable Each variable must be declare before use Each variable has a type: For example int, char, float. int for Integer type; char for character like ‘A’; float for real number;

Example int LuckyNumber=17; float RealNumber; char a=‘A’;

Identifiers Identifier: name of a variable, function, or class Rules for identifiers in C++: 1 Can be made up of letters, digits, and the underscore (_) character 2 Cannot start with a digit 3 Cannot use other symbols such as ? or % 4 Spaces are not permitted inside identifiers 5 You cannot use reserved words 6 They are case sensitive

Self Check 1. What is the type of the values 0 and ‘0’? 2. Which of the following are legal identifiers? Greeting1 g void 101dalmatians Hello, World

Answer int and char Only the first two are legal identifiers

Syntax : Variable Definition typeName variableName = value; or typeName variableName; Example : int number = 12; Purpose: To define a new variable of a particular type and optionally supply an initial value

The Assignment Operator Assignment operator: = Not used as a statement about equality Used to change the value of a variable int number1; int number2, number3; number1=number2=number3=88;

number2=number2-1; number3=number2+1;

How to read a variable #include using namespace std; void main() { int number; cout<<“please enter a number \n”; cin>>number; number=number+1; cout<<“the number is “<<number; }

Integer Types The short, int and long Integer Types A short integer is at least 16 bits An int integer is at least as big as short A long integer is at least 32 bits and at least as big as int.

E.g. A 16-bit int might run from to The sizeof operator returns the size (in bytes)

#include int main() { int n_int = INT_MAX; short n_short = SHRT_MAX; long n_long = LONG_MAX; cout << “int is “ << sizeof (int) << “ bytes” << endl; cout << “short: “ << n_short << endl; cout << “long: “ << n_long << endl; return 0; }

int is 4 bytes Maximum values: –Short: –Long:

Characters and small integers #include int main() { char ch = ‘M’; // assign ASCII code int a = ch; cout << “ASCII code: “ << ch << “ is “ << a << endl; ch = ch + 1; a = ch; cout << “ASCII code: “ << ch << “ is “ << a << endl; return 0; }

Output M is 77 N is 78

Boolean type bool isReady = true; int ans = true; // ans assigned 1 int promise = false; // promise assigned 0 bool start = -100; // true bool stop = 0; // false

Floating-point number E.g We have float, double, long double

Arithmetic operators Summation: + Multiplication: * Division: / Subtraction: -

Operator Precedence int number = * 5 // 35 or 23? float logs = 120 / 4 * 5 // 150 or 6??

Type Casting Conversion between types: (typeName) value // c typeName (value) // c++ e.g. – cout << int(‘A’) << endl; // 65 – float one, –int two; one = ; two = (int) (int) 2.1;