Rather than reading a single word or byte from main memory at

a time, each cache entry is usually holds a certain number of

words, known as a "cache line" or "cache block" and a whole

line is read and cached at once. This takes advantage of the

principle of locality of reference: if one location is read

then nearby locations (particularly following locations) are

likely to be read soon afterward. It can also take advantage

of page-mode DRAM which allows faster access to

consecutive locations.