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Definition

• A small scale size IC's memory chip used to store and access data in any order (i.e. in random order), so the name Random Access Memory.

Description

• Also called as temporary or volatile memory.
• Holds the program and data, which are currently processing.
• Data is lost as soon as computer is turned off or power failure.
• Data stored in this memory can be altered or changed.

Types of RAM

SRAM (Static RAM):

• Fast and has less access time.
• Consists of flip-flop using either transistor or MOS (Mosfet).
• For each bit it requires one flip-flop.
• Status of each bit remains as it is unless there is write operation or power is off.
• e.g. Cache memory.
• Advantages: Refreshing circuit is not required.
• Disadvantages: Costly and low package density, Requires more space.

DRAM (Dynamic RAM):

• Slower and higher access time
• Data is stored in the form of capacitors.
• Capacitors charges when data is 1 and doesn't charge if data is 0.
• Because of leakage current in capacitor, they need to be refreshed to hold the data in memory cells.
• Refreshing is the process in which the contents of each memory cell is read and written hundred times a second.
• This maintains the data of memory cells in capacitor.
• e.g. Main memory.
• Advantages: Cheaper than static RAM.
• Disadvantages: Requires refreshing circuit.