C Language Tutorial on Pointers for Beginners Session - 12 - Elprocus Video Lecture | Basics of C Language - Fundamentals of Programming - Software Development

the 12th session which is of pointers as
I said to take up the concept of
call-by-reference we need to get the
concept of pointers first so we'll take
up what exactly pointers are now a
direction to pointer it is nothing but a
variable which holds the address of
another variable the basic definition of
a pointer is it is nothing but a
variable which holds the address of
another variable so you can three the
pointer is also variable as we say as we
used to say in I now we call is of type
variable likewise pointer is also
variable but it holds the address of
another variable now what do we mean by
address offs another variable the two
operators we use in pointers are we will
be taking up two new operators in this
concept of pointers which is the
ampersand we call it as a dress off
operator and the star we call it as
value at the address operator so these
are the two operators which we are going
to use now declaration declaring and
initializing pointers into I is equal to
three which is the one we have been
using till now the data type and I is
the variable in which we are placing the
value three the declaration does the
compiler result space in memory to hold
the integer value associate the name
eyewitness memory location so the value
three at this location this is what
happens in the compilers memory when we
st. I we are reserving to bite salsa
face because it is of type integer under
the name I and we are placing the
integer value 3 into the variable I so
this is what happens you are reserving
two bites of space whose name is given
as I the location name is referred to I
and the value at that particular
location happens to be three and the
identification
this entire location is unique with the
help of the address of that location so
in star J this is it is a pointer now
when I say int J it is a variable which
takes integer values this is a pointer
which pointer variable which take the
address of another integer variables and
to place the address of another integer
this is how we'll be saying as the sand
I into J that is Jay takes the address
of I so this says place the address of I
which happens to be 6485 into the
variable the pointer variable J and
coming to the addresses the addresses
will not be the same all the time if it
is 6485 here it can be some other thing
for the address of I it is not sure that
all the time I will be getting the same
address for the same variable syntax
this is how you need to follow to get
the address ampersand address off you
call that as address of the variable
name used to get address of variable in
memory star variable name this is a
pointer we call it as value at that
address operations with pointers certain
operations are not at all possible with
pointers that is possible and few are
not possible let us see the possible
operators the following operations can
be performed with a pointer addition of
a number to a pointer subtraction of a
pointer subtraction of one pointer from
another can be performed on a pointer do
not attempt the following operations on
the pointer multi addition of pointers
multiplication of pointer with a
constant division of pointer with a
constant will see what exactly all these
do and do not things on pointers
as usually the standard header file a
function integer I which takes a
variable three now when I say printf
person d gamma I it's clear that i will
be printing the value three what I holds
now if I say ampersand I it's not the
value of I it's the address of I which
happens to be 867 to for the variable I
now saying star and this and I that
means read it value at the address of I
is three again so you will get the
output three and pointer is a variable
star p is a variable in which we can
place the address off I now when I say
printf person d a newline character
comma printf person to your new line
character and star ampersand I now
simply saying p let us see what it gives
as you can see the first statement
ampersand I is giving 8680 value at that
address three and again p 8680 why
ampersand I and PR giving the same
result because the address of I has been
given to the pointer variable P now
wherever I say P it is equivalent to of
a person I that is address of I now if I
say printf
printf % d newline character comma star
p i will be getting the value 3 again
because kenna i can replace ampersand I
with P so this ampersand I is fee and
the star is outside when this can print
three why not this prince three that is
the reason when you say ampersand I into
the pointer variable P you can replace
ampersand I with P as you can see the
address has been changed free wittle
previously it was 8680 no it's 86 84 so
the address keeps on changing now if i
print personally a newline character
coma ampersand p what does this say it
says address of p which is stored no
we're at this stage it is 86 84 so for
each and every variable we have you
declare it holds certain address on the
compilers memory and that address is we
can be given with the help of ampersand
operator now to store the address of P
what is that I need to use is it still
pointer P 1 if it is star p 1 there what
is the difference between star p and
star p 1 this is not possible because
this is a pointer which holds the
address and this is also pointer which
holds the address so to place the
address of a point or not a variable
this time to play C to place the address
of a variable I need single pointer to
place the address of a pointer I need
double pointer now p 1 holds p 1 is
quite same as ampersand p so these two
outputs
give the same the last two outputs have
the sand p it's 8688 which is given to p
1 therefore p 1 also gives 8688 now if i
say gamma star p 1 i will be getting
value at the address at p1 what does p1
hold p 1 holds address off p the value
at address of P is ampersand I so the
first statement and last statement will
be the same output the first statement I
am person died and the last statement
will be the same outputs come at double
star p 1 gives trace it in this way p 1
holds a dress off p a value at the
address of p which is a dress of i value
at address of I is nothing but the value
of 3 again so the last output gives 3 so
likewise there is no end for me to store
say the pointers address off p 1 can be
given to triple star p to address off p
2 can be given 24 starts p3 address of
p3 can be given to five starts before so
there is absolutely no and for me to say
the pointer types coming to the
operations with pointers pointer
arithmetic addition of a number to a
point at subtraction of a pointer
separation of one pointer from another
so this we can see in the concept of Rs
arrays and pointers there will be take
up what is addition of a number to a
point of subtraction of a pointer and
all those things as well as will try to
do all these operations which says do
not
attempt the following but still will try
and see what exactly happens when we go
for this