Memory

• consists of electronic components that store instructions waiting to be executed by the processor, data needed by those instructions, and the results of processing the data.

• Each location in memory has an address.

• Memory size is measured in kilobytes (KB or K), megabytes (MB), gigabytes (GB), or terabytes (TB).

TYPES OF MEMORY

       Volatile

• when the computer's power is turned off,volatile memory loses its contents.
• volatile memory is temporary.
• RAM is the most common type of volatile memory.

       Nonvolatile

• nonvolatile memory does not lose its contents when power is removed from the computer.
• nonvolatile memory is permanent.
• examples of nonvolatile memory include ROM.

      Volatile memory : RAM

• RAM chips usually reside on a memory module and are inserted into memory slots.
• The amount of RAM necessary in a computer often depends on the types of software you plan to use.

Types of RAM

*DRAM (Dynamic RAM)-chips must be re-energized constantly or they lose their contents.

*SRAM (Static RAM)-chips are faster and more reliable than any variation of DRAM chips. Are much more expensive than DRAM chips.

*MRAM (Magnetoresistive RAM)-a newer type of RAM, called magnetoresistive RAM (MRAM pronounced EM-ram), stores data using magnetic charges instead of electrical charges.

Nonvolatile memory : ROM

• Read-only memory (ROM) refers to memory chips 
  storing permanent data and instructions.
• The data on most ROM chips cannot be modified.

Types of ROM

*PROM (Programmable Read-Only Memory)-is a blank ROM chip on which a programmer can write permanently.

*EPROM (Erasable Read-Only Memory)-These chips can be erased and rewritten a number of times.

*EEPROM (Electrically Erasable Programmable Read-Only Memory)-Allows a programmer to erase the microcode with an electric signal.