I guess this would be helpful,
/******for a static array********/
char inp[4];
for (n=0;inp[n];n++)
; //do nothing inside the loop
cout<<n; //n will display the number of elements in the array inp[]

/******for dynamic array********/
char *arr = new char [sizeof(char)];
for (n=0;arr[n];n++)
; //do nothing inside the loop
cout<<n; //n will display the number of elements in the array arr[]