What is a pointer Explain pointer arithmetic malloc function in C programming with an example

A pointer in C is the address of variable of a function. The advantages of a pointer over using normal variables are:

If you pass the pointer to a variable to a function, then that function can modify the value of the variable directly.

                Pointer variables can also be used in arithmetic expressions. The following operations can be carried out on pointer:

1.       Pointers can be incremented or decremented to point to different locations like

ptr1=ptr2+3;

ptr++;

--ptr;

2.       If ptr1 and ptr2 are properly declared and initialized pointers, the following operations are valid.

res=res+*ptr1;

*ptr1=*ptr2+5;

prod=*ptr1**ptr2;

quo=*ptr1/*ptr2;

3.       Expressions like ptr1==ptr2,ptr1<ptr2 and ptr2!=ptr1 are permissible provided the pointers ptr1 and ptr2 refer to same and related variables. These comparisons are common in handling arrays.

A block of memory may be allocated using the function malloc. The malloc function reserves a block of memory of specified size and returns a pointer of type of void. This means that we can assign it to any type of pointer. It takes the following form:

                ptr=(cast-type *) malloc(byte-size);

ptr is a pointer of  type cast-type. The malloc returns a pointer to an area of memory with size byte-size

Example:

                                                x=(int *) malloc(100 *sizeof(int));