Pointers

Using the reference operator & and the dereference operator *, we can create and work with pointers.

A pointer is a data type, just like int, char, or double. The pointer is designed to store an address, which you can obtain using the & operator. To declare a pointer, prepend it with the * character.


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int* intPointer; // pointer to an int variable
double* doublePointer; // pointer to a double variable
char* charPointer; // pointer to a char variable

In essence, a pointer is a variable that holds the address of another object.


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int x = 100; // variable
int* pX; // pointer to an int variable
pX = &x; // pX now points to x

Note

Typically, pointers are named by prefixing the letter p to the name of the object they're pointing to.

When you dereference a pointer, you access the value of the variable it points to.

Main

#include <stdio.h>

int main()

{

int x = 22543; // variable

int* pX = &x; // `pX` is pointer to `x`

printf("The value of `pX` is %p\n", pX); // value of pointer `pX`

printf("The value of `x` by pointer `pX` is %d\n", *pX); // pointer dereference

return 0;

}


              1234567891011121314
            
#include <stdio.h>

int main()
{
    int x = 22543; // variable
    
    int* pX = &x; // `pX` is pointer to `x`

    printf("The value of `pX` is %p\n", pX); // value of pointer `pX`
    
    printf("The value of `x` by pointer `pX` is %d\n", *pX); // pointer dereference
    
    return 0;
}

Note

*(&variable) == *pVariable

If you attempt to dereference a null pointer, the compiler will raise an error:

Example provided to showcase the mistake

Main

#include <stdio.h>

int main()

{

int* pX;

printf("x = %p", pX);

return 0;

}


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#include <stdio.h>

int main()
{
    int* pX;

    printf("x = %p", pX);

    return 0;
}

Aufgabe

Swipe to start coding

Determine the size of int and double pointers.

Lösung

#include <stdio.h>

// You may use `%d` specifier for `sizeof()` function

int main()

{

int* pInt;

double* pDouble;

printf("Sizeof `int*` = %d, sizeof `double*` = %d\n", sizeof(pInt), sizeof(pDouble));

return 0;

}

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Abschnitt 6. Kapitel 3

#include <stdio.h>

// You may use `%d` specifier

int main()

{

___ pInt;

___ pDouble;

printf("Size of `int*` = %d, size of `double*` = %d\n", ___(pInt), ___(pDouble));

return 0;

}

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