Primary and Secondary Storage

It refers to internal computer memory that is accessed by the CPU

• RAM (Random Access Memory) • ROM (Read Only Memory • Cache Memory

RAM (Random Access Memory) is volatile, fast-access memory that temporarily stores data currently in use

ROM (Read Only Memory) is non-volatile, read-only memory that contains permanent instructions used by the computer when it boots up.

Cache is volatile, very fast-access memory which stores frequently used instructions that is situated in or next to the CPU.

It refers to memory that retains its contents when the computer is shut off. When you run a file, it is copied from secondary storage into primary storage and when you save a file, it is copied from primary storage to the secondary storage.

• Primary storage is directly accessed by CPU, whilst Secondary storage is not • Primary storage is volatile, secondary storage is non-volatile • Primary storage has a small capacity, Secondary storage has a large capacity

• Magnetic Disk coated with magnetic material where different areas can be magnetized North or South to store binary digits 1 or 0 • Optical Different areas reflect or do not reflect laser light differently to store binary digits 1 or 0 • Solid State Semi-conductor material where different areas act as switched, open or closed, to store binary digits 1 or 0

• Flash • SSD

PROS: - Very fast to access CONS: - Moving parts mean they are more susceptible to failing due to physical shock - Data can be wiped out by a magnet - High power consumption

• CD • Blu-ray • DVD

PROS: - Portable - Cheap to produce CONS: - Small memory capacity - Slow data transfer

The disk rotates while a laser beam burns indentations into the surface which are called pits. The space between the pits are called lands. The pits and lands represent binary values (1s and 0s)

PROS: - Less susceptible to physical shock - No noise - Higher capacity compared to same volume of HDD CONS: - Data can not be overwritten - Limited amount of write operations

It is stored in server farms and data warehouses

PROS: - Access data anywhere CONS: - No internet means no access - More vulnerable to cybercrime - Potentially expensive

When RAM is full, there needs to be a way for CPU to activate instructions that are not currently available in RAM To do this: - An area of memory in secondary storage is found - Inactive instructions in the RAM are moved to that area of memory in secondary storage - Required instructions from secondary storage are copied into CPU - CPU now has access to the instructions it needs - Once the process is complete, instructions can now be moved back into RAM from secondary storage

Flash memory uses floating gate to store electrons, allowing individual gates to have a value of 1 (No electrons) or 0 (Some electrons). Change in voltage applied to the gate allow electrons to pass through the isolation layer and into or out of the floating gate.