Day_3

Things I learned:

& operator in c++(pointer 1st video):

& operator provides address of a mentioned variable. But it dont work for charecter type variables.

For int type:

int main(){
    int intgr = 3;
    cout<<&intgr;
}

For float type:

int main(){
    float flat = 13.2;
    cout<<&flat;
}

For cahr type:

int main(){
    char charecter = 'A';
    cout<<&charecter; 
}

This will output A, because if you pass address of a char type variable in cout<< then it returns the stored object in variable itself.

Solution: &charecter has a type of char* and we need to change it to void* using typecasting. By doing that cout<< dont get to know what type of address it is, so it prints the address.

int main(){
    char charecter = 'A';
    cout<<(void*)&charecter; 
}

Pointers:

Pointer is a variable which stores address of another variable.

Data type of the pointer variable should be same as the main variable. Size of a Pointer variable:

The size of a pointer in C/C++ is not fixed. It depends upon different issues like Operating system, CPU architecture etc. Usually it depends upon the word size of underlying processor for example for a 32 bit computer the pointer size can be 4 bytes for a 64 bit computer the pointer size can be 8 bytes. So for a specific architecture pointer size will be fixed.
It is common to all data types like int *, float * etc.

PS: Read about Dereference Operator.

Array Pointers:

int A[] = {2,4,5,8,9};
int *ptr;

prt = A  
cout<<ptr<<" "<<A; // Address of A[2] -> the 1st element

cout<<*ptr         // Prints the element stored in A[2], 
                   //its called dereferencing

cout<< ptr+1;        // prints the address of 2nd element

cout<<*(ptr+1)       // prints the 2nd element

In array pointer, you stores the address of the 1st element by providing the array name(here its A) in an pointer array. Then to access the other elements by incrementing the pointer and dereferencing it one by one (I mean *(p+1)). Dereferencing means adding * with a pointer variable. This helps to get the element stored.

Passing array in a function:

void fun(int *arr,int n){
    ...
}
int main(){
    fun(arr, n);
}

Passing a variable in a function:

void fun(int *x){
    ...
}
int main(){
    fun(&x);
}