how to check that a array of some data type(let's say int ) has been assigned some value at random positions if size of array is any(let's say 10).

If you want to find out garbage values (or non-garbage values), first, you must define what is a garbage value.

Eg:- If your array will only have unsigned values then you can use a negative value (-1, -2, -3....) as your garbage value.

int arr[10];
int garbage = -1;

//initialize your array
for(int i=0; i < 10; i++)
{
   arr[i] = garbage;
}

//now test for garbage
for(int i=0; i < 10; i++)
{
   if(arr[i] == garbage)
   {
      //do something with this piece of garbage
   }
   else
   {
      //it's not garbage and do something else
   }
}

Alright pal, now this method works fine, but what if I can't use any value in the range of int as the garbage value ?

Well, for this case, the following approach is suitable. Just read the following code, you'll understand the mechanism.

typedef struct {
   int value;
   bool is_used; //if this is true then the 'value' is not garbage.
}MyArray;

MyArray arr[10];

//initialize your array
for(int i=0; i < 10; i++)
{
   arr[i].value = 0;
   arr[i].is_used = false;
}

//test for garbage values
for(int i=0; i < 10; i++)
{
   if(arr[i].is_used == true)
   {
      //not garbage, do something
   }
   else
   {
      //garbage, do something else
   }
}

The first approach if more efficient when you know the range of your valid input values, if not the second method is more clear, simple and understandable.