CODEWITHSUNDEEP
cpointers
Seyon Seyon
Seyon Seyon

Reputation: 567

Correct way of declaring a pointer with value

I want to learn very basics of pointers in C language

What is the difference between below two ways? Which is correct? Which is more preferable?

int a = 20;
int *p = &a ;

or

int a = 20;
int *p ;
p = &a ;

Upvotes: 1

Views: 194

Answers (1)

bk_32
bk_32

Reputation: 529

The difference here is not related to pointers, but to declaring and initializing variables in general.

For example, you can do:

int a; // this declares the variable a as an integer
a = 20; // this initializes the variable a with the value 20.

OR, you can combine these two into one line:

int a = 20;  //this now both declares and initializes the variable a.

The difference is that you can only declare a variable ONCE, but you can assign a value to it as many times as you like.

So if you were to write

int a = 20;

and then later on in your code you wanted to change the value of a to say, 30, here you can ONLY write

a = 30;

You could not write int a = 30; again, because you cannot declare a again, a has already been declared.

This difference is what you are illustrating with your pointers.

int a = 20;  //variable a is declared as an int and also initialized to the value 20
int *p = &a ; //pointer p is declared and initialized with the address of a.
or
int a = 20; // variable a is declared as an int and also initialized to the value of 20
int *p ; // pointer p is declared
p = &a ; // pointer p is assigned the value that is the address of variable a.

You could also have written

int a;
a = 20;
int *p;
p = &a;

And this is still correct, and produces exactly the same result.

Upvotes: 1

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