Which database can be used on a desktop computer ?

What operating system is a smartphone most likely to use? 1.bsd 2.mac os x 3.symbian 4.linux

The width of a piece of rectangular land is 5m shorter rhan 1/3 of its length .find the width of the land if the length is 60m,150m.

Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?