Pointers and arrays are very closely linked in C.
Hint: think of array elements arranged in consecutive memory locations.
Consider the following:
Fig. Arrays and Pointers
To get somewhere in the array (Fig. ) using a pointer we could do:
pa + i a[i]
WARNING: There is no bound checking of arrays and pointers so you can easily go beyond array memory and overwrite other things.
C however is much more subtle in its link between arrays and pointers.
For example we can just type
pa = a;
pa = &a
a[i] can be written as *(a + i). i.e. &a[i] a + i.
We also express pointer addressing like this:
pa[i] *(pa + i).
However pointers and arrays are different:
This stuff is very important. Make sure you understand it. We will see a lot more of this.
We can now understand how arrays are passed to functions.
When an array is passed to a function what is actually passed is its initial elements location in memory.
This is why we declare the function:
~int strlen(char s);
An equivalent declaration is : int strlen(char *s); since char s char *s.
strlen() is a standard library function (Appendix ) that returns the length of a string. Let's look at how we may write a function:
Now lets write a function to copy a string to another string. strcpy() is a standard library function that does this.
This uses pointers and assignment by value.
NOTE: Uses of Null statements with while.