Getting Started

Chapter 8: C Pointers and Arrays

create pointers that point

iscipline, however, pointers can also be used to

o buffer of an IBM PC. I made

is, I started a count with 1 instead of 0, and wrote

last data byte to an address that was one byte outside of the video buffer. That

e was only occasionally important enough to crash the system. When your

ittently with no apparent rhyme or reason, you may well

suff d bug to find.

tored data) that contain the address of other variables

ters to data, pointers to pointers, pointers to

le and clear as possible

ceding its name with an *, called the

&, called the address operator:

ve two worse choices been made for

mbol d for

f the variable name

could have been written to require that

e suffix follow the pointer everywhere, thus helping us know what we are

ling with. But NOOOO.... * and & were chosen, and confusion reigns eternal.

e could fix this problem by adding a couple of defines to alias the * and & as ptr

addof, and we could require that we always name pointers in such a way that

, but since our goal is to learn C as Ritchie and

NSI intended and not my version of C, we’ll do it the hard way. What? you

when they are used carelessly, and it is easy to
somewhere unexpected. With d
achieve clarity and simplicity.”

I once used a pointer to sequentially access the vide
a simple ‘fence-post’ error, that
the
byt
computer crashes interm
be ering from a bad pointer use. It can be a damn har

To recap: variables (RAM s
are called pointers. You can have poin
pointers to pointers to... but let’s try to keep it as simp
(whoops... too late).

We declare a variable to be a pointer by pre
indirection or dereferencing operator:

int *q; // q is a pointer to an int

We get the address of a variable using

q = &v; // put the address of v in the pointer q

Never in that annals of mnemonics ha
sy s. Instead of *, the letters ‘ptr’ could have been chosen
in the second use o

for pointer, an
&, the letters ‘addof’. There is no indicator
‘q’ that it is a pointer, but the compiler
som
dea
W
and
we always know it is a pointer
A
don’t think it will be hard to remember what the * and & do? Wait till you run
into things like: