C++ quik notes

2. Sizeof:- time operator sizeof is a unray compile time
operator that returns the length of variable or
parenthesized type specifierthat it precedes.
ex:- sizeof (type) [where type is c++ datatype]
ex:- sizeof(int);
The comma operator
a pair of expressions separated by a comma is evaluated
left to right.
Z= (a=1, a+5) / * bracket evaluates 6 and thus is the value
assigned to Z.

3. Type casting
The process of converting one predefined type into another is called type casting.
type conversion have two forms:-
implicit type conversion
explicit type conversion
Implicit type conversion:- the process of converting one predefined type into
another performed by compiler without programmer’s intervention. it is applied
generally whenever different data types are intermixed in an expression.
ex:- long double
It either operand is of type long double the other is converted to long double.
Explicit type conversion:- Explicit type conversion is user defined that forces an
expression to be a specific type.
ex:-void main ()
{
int x=65;
cout<<x<<endl;
cout<<(char)x; //explicit type casting
}
output:- 65
A

4. C ++ shorthands
C++ offers special shorthands that simplify the coading of certain type
of assignment statements.
ex:- a=a+10
can be written as,
a+ =10
some examples of c++ shorthands:-
X- =10 Equivalent
to
X= X-10;
X*=3 Equivalent to X=X*3;
X/=2 Equivalent to X=X/2
X%=z Equivalent to X=X/Z

5. Properties of variable can be describe by two ways:-
Data type
Storage class specifier
Complete declaration for variable:-
Storage_ class_ specifier datatype variable name;
FOUR TYPES OF STORAGE CLASS SPECIFIER:-
Automatic (local to block)
When variable are declared in the beginning of a block they are automatically
created by assigning the memory. The values of such variable are garbage.
Therefor they are also called automatic variable. All such variable gets destroyed
whenever their scope ends.
Eg:-
void fun
{
int a; /* local to fun block*/
}
Void fun1
{
int a; /* local to fun1 block*/
}

6. Static – a variable when declared static gets initialized by zero or by
a specific value only for the first time at the time of declaration. Such
variable retain their value throughout the life time of variable.
void ()
{
int i, sum=0; //sum is declared as static variable
for (i= 0; i<=10; i++)
{
sum= sum +i;
}
cout<<”nSum is =”<<sum;
}
Extern:- variable when defined outside the program file but used in
the current file are used after linked them using extern keyword in
declaration.
Register:- its concept is in low level programming language there is
no any use in high level language.

7. Global ( outside all scope)
When variable is declared outside of all scope as it is visible
throughout the main program and its associated function with
specific value are initialized by zero ,
int a ; /* global variable*/
void main ()
{ }
Scope resolution operator(::) - When name of local and global
variable is same then to distinguish between these two variables
we use scope resolution operator it denotes global variable only.
Ex:-
int a = 10 ; /* global variable*/
void main ()
{
int a = 100; /*local variable */
cout<<”a = ”<<a<<” “<<”::a =”<<::a;
}
Output:-a = 100 ::a = 10