Dynamic random access memory (DRAM) is the majority in computers. Modern computers use several types of DRAM. Before 2002, most computers used single data rate (SDR) RAM. Most computers made since then use either double data rate (DDR), DDR2, DDR3, or RAM. The later types allow stored data to be moved and used more quickly, so that the computer's processor can keep working quickly without having to wait for data as long or as often. 