Primary Storage

- Digital data stored in bits – BInary digiTs
- Combination of 8 bits is called a byte
- Different combinations of bits represent different symbols
   - ASCII
   - EBCDIC
- All data and programs are represented in bits
   - Video
   - Pictures
   - Text
- The main memory of the computer
- Stored on semiconductor chips
   - RAM – random access memory
      - Volatile
      - Cache memory
         - Internal – ultra high speed and VERY expensive
         - External – very high speed and less expensive than internal cache
   - ROM – read only memory
      - Non-volatile
- Primary storage holds all programs that are running and the data those programs use

Data Storage Units

Name	Storage Amount	Approximate Equivalent
Byte	String of 8 bits	1 character
Kilobyte	1.024 bytes	½ typewritten page
Megabyte	1.048.576 bytes	1 digital picture
Gigabyte	1.073.741.824 bytes	Beethoven's 5th Symphony on CD
Terabyte	1.099.511.627.776 bytes	2.000 CD
Petabyte	1.125.899.906.842.624 bytes	160.000 DVDs(more than half of all theatrical releases)
Exabyte	1.152.921.504.606.846.976 bytes	½ the amount of information generated in a year(5 exabyte = all words ever spoken by human beings)
Zettabyte	1.180.591.620.717.414.303.424 bytes	As Much data as grains of sand on all the world's beaches
Yottabyte	1.202.925.819.614.629.174.706.176 bytes	As much data as the number of atoms in 2 tablespoons of water