Static RAM (SRAM)- Static RAM is a type of random access memory that is used to hold data without external refresh circuitary to keep the data together. The memory is held for as long as there is power supplied to the circuit.
Dynamic RAM (DRAM)- Dynamic RAM only holds data if a refresh circuit has continuous acess to the Dynamic RAM. The refresh circuit reads each memory cell even if the cell being scanned has no information stored in it, this refreshes the memory contents. this process is repeated hundreds of times per second. If this process is not repeated, the Dynamic RAM loses its memory even if power is still supplied. This process gives the name Dynamic. All PC’s use Dynamic RAM for their main system memory.
Static RAM and Dynamic RAM compared.
· Static RAM doesn’t require external refresh circuitary to help to retain the data stored whereas dynamic RAM needs external refresh otherwise the data stored is lost.
· Static RAM is faster than Dynamic RAM
· Dynamic RAM is more complicated than Static RAM due to the external refresh circuits required
· Dynamic RAM is cheaper than Static RAM
· Static RAM is larger than Dynamic RAM because Static RAM is made up of four or more transistors per bit whereas Dynamic RAM uses one transistor and a capacitor.
Read Only Memory (ROM)- ROM is a type of memory that can only be read and is used in PC’s. the data stored in ROM is permanently present with or without power connected. ROM can be removed, stored for a long period of time and replaced without the data being lost which makes ROM non-volatile, whereas RAM is volatile memory.
Parallel ports- a parallel port is an interface found on computers and are used to connect peripherals to the computer.