1.2 Memory

1.2 Memory

1. FLASH MEMORY

   • gets lost easily
     • non volatile
     • expensive
       • portable
         • fast access
   • uses
     • USB Drives, memory cards, SSD
       • used when settings need to be retained when power is off

2. SOLID STATE

   • e.g. SD card, memory stick
     • uses flash memory
       • non rotating parts
         • low capacity
           • high cost
     • reliable

3. POST(CHECKS)

   • BIOS chip checks if system works
     • checks if all components are present and functioning correctly
       • if test fails, error message
         • checks completed, CPU starts OS

4. VIRTUAL MEMORY

   • simulated memory on hard drive
   • why?
     • disk thrashing
       • when a computer's virtual memory subsystem is in a constant state of paging
         • holds programs open but not currently in use
           • allows programs to be open at the same time
             • holds programs when RAM is full
   • how is it implemented?
     • VMM creates file on hard disk
     • move data between RAM and VM
     • swapping/paging

5. ROM

   • holds operating system
     • can't be accidentally changed
       • data is pre-written and comes with com
         • can be hacked
           • virus attack unlikely
             • data remain whether on/off

6. RAM

   • expensive
     • volatile
       • data not permanently written
         • stores data/programs currently in use

7. CACHE

   • small amount of memory
     • doesn't hold a lot of info