Concept of the Pointer

Pointers in C programming

Theory:
Pointer – Pointers are variables that hold a memory location.   
   Pointer is a variable that contain the address of another variable.Every Location has a number associated with it, it is called as an address. 

The Symbol '&' Ampersand is used to represent the address.

The Symbol '*' is used to represent a pointer. It is called the dereferencing or indirect operator.

int *p;  here p is a pointer variable. Its size is 4 byte and it accept the address of integer variable.

For float , char etc. we can type.char *ch;float *ft;double *db;Each one of them will get same size of the memory i.e. 4 bytes.  

Harold Lawson is credited with the invention of the pointer, PL/I the first Procedure Oriented Language(POL) supported pointer in 1964.

Program snapshot:

Declaration of a Pointer : 

     Declaration of a pointer is nothing but assigning a memory location. And Letting our compiler known about the variable, what is its data type , its value , and address of memory location.

Pointer with printf() Statement

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printf(“\n%u\n”,*p);

The above statement will print the value at the address stored in P pointer.

As we know P is a pointer and according to the definition, it contain the address of a variable.

Working of printf(); :

printf() statement require

1) Format Specifier e.g. %d , %u, %f etc.

2) Data to print. E.g. “Hello World! ”, 10 , -123 etc.

If we write

printf(“\n%d\n”,P);

This is a  valid statement, but the content of P will be echoed on the console , and content of P is the address of variable n.

*P -> will give the Value stored at the address in the pointer.

SNAPSHOT

Pointer with scanf() Statement

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scanf() statement is used to accept the input from the user via i/o devices.

scanf() function require:

1) Format Specifier.

2) Address of the memory where value to be stored.

FORMAT

scanf(“%d”,p); -> Here p will provide the content. i.e the address of n.

so we can directly type P in scanf() function.

Lets see other options.

1) *p

2) &p

3) P

1) *p : It will give the value at the address it content. i.e 10

So the statement will be

scanf(“%d”,10); | as p -> address of n , and n content 10;

So when the scanf() function encounter it will hang.

2) &p : It will give the address of variable p.

As P is declared as pointer, so we can’t store any value in p except the address of other location.

So this will give error.

3) P : p will give the its content, which is nothing but the address of the other local variable i.e. n.

So this is valid statement.

scanf(“%d”,1654200); This will store the user entered value at the address 1654200 , i.e. in n.