Vectors_DMA.txt

VECTOR:
    vector<dataType> name({ value1, value2, value3 ....}); 
    vector<dataType> name(size, value); 
    vector<dataType> arrayName; 

    DataType here can be of type className.
    We can create array of elements each of type a class.
    vector also starts with index 0.

CLASS: 
    Class must have both private and public sections.

STRUCT:
    Same as class but donot have any public and private sections. All are public by default.


To access the values or functions of the class or struct:
    call it as -- classElement.value 
               -- classElement.function


To CALL CONSTRUCTOR:  
// calling inside the class method-1
    ClassName(): variable(value) {}

// calling inside the class method-2
    ClassName (list-of-parameters){
        // assigning values or instructions
    }

// calling outside the class
    <class-name>::<class-name>(list-of-parameters){
        // assigning values or instructions
    }


To CALL DESTRUCTOR: 
// calling inside the class
    ~ClassName() {
        //some instructions
    }

// calling outside the class
    ClassName :: ~ClassName(){
        //some instructions
    }


DYNAMIC MEMORY ALLOCATION::
FOR CREATING A BLOCK OF MEMORY:
    int *p = NULL;
    p = new int;
    (or)
    int *p= new int;
    (or for an array)
    int *p = new int[10];
We can give this pointer a new allocation of the data

FOR REMOVING THE ALLOCATED VARIABLE:
    delete pointer-variable; // programmer responsibility to delete the dynamically allocated memory
    (or)
    delete[] p; // deletes the array pointed by the p

ERRORS IN DYNAMIC ALLOC:
int *p = new(nothrow) int[10]; //if the allocation fails it shows error of type bad_alloc
// to get rid of that error and let the program cntinue we use this
// alloc fails when there is not space for the new alloc 
// in that case it alloc the new one to nullptr and let the program run.

EXPLANATION ABOUT NEW KEYWORD:
int *b= new int; // this shows that the new keyword gives new pointer to particular storage of memory
// when we say new int , b contains the address of the new 4 bits storage allocated, it points to the first bit.