Arrays using Pointers..

In this blog let’s try to understand about pointer.  So, what is pointer?... pointer is thing that used to point something in a group. For example,

Here, the pointer is used to point the temperature in the gauge.

Similarly, in computer the data gets stored in memory and each data is assigned with an address in the memory. So, the pointer is used to point the data, in other words pointer contains a memory address of that particular data. (int a = 10; here the ‘a’ indirectly act as a pointer which has the value ‘10’.) Now we can see that how arrays are similar with pointer. We know that array is a continuous block of memory that stores multiple data of same kind. Let’s have a close look

In c program pointer a declared with ’*’  symbol followed by a variable (eg : int *ptr).

int a[10];---------------------------( 1 )------------------> this array stores 10 integers at max, here all elements in array is referenced with the variable ‘a’. which is more less equal to pointer. So by using pointer concepts we can create a dynamic array.

Int *p=( int * ) malloc ( x*sizeof(int));-----------------( 2 )-----------> here the x is the count of elements that user provides during runtime. (int *) is used instead of (int) because return type is a pointer variable. Malloc is a dynamic memory allocation that allocates required size of bytes and return the pointer that points at first position. (x*sizeof(int)) is used define memory space required ‘x’ is user defined value and ‘sizeof()’ is function that returns the size of a datatype of variable that passed as its parameter, here ‘int’ is passed. If user’s  x value is 10 then its creates 10 blocks of memory each with the size of int. So, from above explanation we understood that both (1) and (2) are more or less same.

Now you can ask that Java does not support “pointers”. Yes of course JAVA does not support pointers at user level but at inside its JVM pointers are used. So it is worthy to know about it.

In two dimensional array , int a[10][5]-------------(3)-------------> here, ‘10’ independent blocks each of size ‘5’ gets created and first value(here, 10) act as a index value. Here double pointers are used, the pointer which contains address of another pointer is called as double pointer. Its is represented as ** symbol followed by variable, (eg **a). Now let’s look at how the two-dimensional array is stored in memory. 

                                                      Here, the “A” act as a double pointers which points to the address block of pointers A[1],….,A[10] which pointes to the block that contains actual data, thus arrays are similar to pointers.

I hope you could get some idea about pointers...any queries comment below and do subscribe for more blog's

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