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Secondary Memory

Secondary memory is where programs and data are kept on a long-term basis. Common secondary storage devices are the hard disk and optical disks.

A hard disk might have a storage capacity of 500 gigabytes (room for about 500 x 109 characters). This is about 100 times the capacity main memory. A hard disk is slow compared to main memory. If the processor interacted with it directly the entire computer system would slow down. The reason for having two types of storage is this contrast:

Primary memory Secondary memory
  • Fast
  • Expensive
  • Low capacity
  • Works directly with the processor
  • Slow
  • Cheap
  • Large capacity
  • Not connected directly to the processor


Say that you have purchased the game Doom IV and have installed it on your computer. The game consists of

After installation, where is each of these parts located in your computer system?