Solid-state storage magnetic storage
optical storage
read-only memory
random access memory
represents data as 1 or 0 by changing the
alignment of tiny Iron particles on its surface
stores data by correlating the absence or
presence of light with the binary system
similar to RAM but with a special circuit
to retain data when powered off
stores data that the CPU is working on at
any given point of time
stores non-changeable instructions for
starting up a computer

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)?