Main Memory (RAM, ROM and Cache)

• Primary Storage


  Very quick because it is directly accessed by the CPU, typically smaller in storage size, sometimes called 'main memory', includes RAM and ROM
• Secondary Storage


  Slower because it is not directly accessed by the CPU, typically larger in storage size, used for long-term storage of data and files because it is non-volatile, includes magnetic, optical and solid state storage
• Volatile storage


  Temporary - data is lost whenever the power is turned off, example: RAM
• Non-volatile storage


  Saves the data even when not being powered, data can be stored long-term and accessed when the computer is switched on, example: ROM
• Primary storage is low-capacity, internal storage that can be directly accessed by the CPU
• Program instructions and data must be copied from the hard drive into RAM to be processed by the CPU because primary storage access speeds are much faster than secondary storage devices like the hard drive
• Random Access Memory (RAM)

  Volatile (temporary) storage that stores all programs that are currently running, also stores parts of the operating system to be accessed by the CPU, made up of a large number of storage locations each with a unique address
• Read-Only Memory (ROM)


  Non-volatile storage that cannot be changed, stores the boot program/BIOS for when the computer is switched on, the BIOS then loads up the operating system to take over managing the computer
• Virtual Memory


  If there is insufficient space in RAM for all programs, the computer can use the hard disk drive (HDD) as an extension of RAM, unused data in RAM is moved to the hard drive so new data can be transferred into RAM, when required the data can be moved back from virtual memory into RAM, using virtual memory allows users to run more programs simultaneously with less system slow down