Memory

The data and the programs are stored in binary format in computer's memory. Memory is organized in bytes, where 1 byte = 8 binary digits. In practice we use multiples of byte.

1 Kb	1024 bytes	bytes
1 Mb	1024 Kb	bytes
1 Gb	1024 Mb	bytes

There are several physical memories in a computer; they form a memory hierarchy. Note that the physical chips for cache memory use a different technology than the chips for main memory; they are faster, but smaller and more expensive. Also, the disk is a magnetic storage media, a different technology than the electronic main memory; the disk is larger, cheaper but slower.

Memory Type	Size	Access time
Registers	8 bytes	1 clock cycle
Cache, Level 1	126 Kb - 512 Kb	1 ns
Cache, Level 2	512 Kb - 8 Mb	10 ns
Main memory	8 Mb - 2 Gb	60 ns
Hard drive	2 Gb - 40 Gb	10 ms