Primary memory
PRIMARY MEMORY: RAM AND ROM
•RAM (Random Access Memory) is volatile (temporary). Programs and data can be written to and erased from RAM as needed. This means that RAM does not retain its bit configuration when the power is turned off, but ROM does
•ROM ( Read Only Memory) is nonvolatile (permanent). The contents in locations in ROM cannot be changed
•It holds instructions that run the computer when it is
first turned on (BIOS)
•The CPU accesses each location in memory by using a
unique number, called a memory address.
Memory types- RAM
•RAM: random access memory
–SRAM: static RAM
•No need to be refreshed
–DRAM: dynamic RAM
•Need to be refreshed periodically
•Main memory
–SDRAM (Synchronous DRAM)
–EDRAM (Enhanced DRAM)
–EDO (Extended Data Out)
–FLASH RAM
–Ferroelectric RAM
Memory types– ROM
•ROM: read-only memory (Pre-programmed)
–PROM: programmable ROM
•Only written once
–EPROM: erasable PROM
•Use ultraviolet light to erase data
–EEPROM: electronically EPROM
•Can be erased using electronic impulses (higher voltages)