Memory

Memory

1. RAM

   • Known as main memory
   • Volatile - data lost when no power supply
   • Needed for OS, loading apps and data in use
   • When program loaded, copied from hard drive into RAM, so CPU can access data
   • The more RAM, the faster the computer
   • Can read and change data in RAM
   • Types of RAM
     • Dynamic RAM - has transistor and capacitor, holds charge every few milliseconds to represent one bit, refreshes every few milliseconds
     • Static RAM - 4 or 5 transistors wired together so do not lose charge, store data when have power, faster as not constantly refreshed, used as cache memory

2. ROM

   • Non-volatile, read only memory
   • Basic instructions to start up computer stored in ROM
   • Read only - cannot be changed
   • ROM chip attached to the motherboard
   • ROM is quite slow

3. Flash Memory

   • Non-volatile
   • Used in USB sticks, memory cards, mobile phones, video games hardware and more
   • Solid state device - keeps data without power and no moving parts
   • Data and programs can be accessed very fast
   • Reviving data is slower than hard disk, as limited by connection

4. Virtual Memory

   • Computer will slow down if RAM fully used
   • If not enough RAM, part of HDD used (virtual memory)
   • Slows down computer as data must be transferred
   • If more RAM installed, computer becomes faster as more space

5. HDD

   • Permanent storage of programs and OS
   • Very slow, so program put in RAM when used as faster
   • Made of hundreds of thousands of tiny magnetic disks