COMPUTER MEMORY BASICS

Computer memory means storage of data and instructions required during the processing of data and output results.

TYPES OF MEMORY

- Primary / Main Memory

- Secondary / Auxiliary Memory


PRIMARY MEMORY

• The memory unit that communicates directly with the CPU.
• Allows the computer to store data for immediate manipulation.
• Keep track of what is currently happening.
• VOLATILE in nature ( When computer is turned off, it is lost ).

TYPES OF PRIMARY MEMORY

- Random Access Memory

• Dynamic RAM
• Static RAM 

- Read Only Memory

• Programmable ROM ( PROM )
• Erasable ROM ( EROM )
• Erasable Programmable ROM ( EPROM )
• Electrically Erasable Programmable ROM ( EEPROM )

SECONDARY MEMORY

• Data is not directly processed by CPU.
• Used to store data and programs when it is not in use.
• Stores much larger amount of information.
• NONVOLATILE ( It is retained and not lost even if the computer is switched off. )
• Are basically storage devices.

Secondary Memory Storage Devices

• Magnetic discs - HDD, Memory Stick, Floppy.
• Optical Disks - CD, DVD, Blue ray discs.
• Pen drives.

MEMORY HIERARCHY

• Computer uses hierarchy in a manner to enable the fast speed and large capacity.
• CAPACITY and ACCESS TIME are two key factors.
• Lesser the access time, faster is the speed of memory.

CPU-->REGISTER-->CACHE-->MAIN MEMORY-->MAGNETIC DISK-->MAGNETIC TAPE

MEMORY MEASUREMENT

BIT - Binary Digit means 0 or 1

BYTE - means one character ( a letter, a symbol, a number, a group of 8 bits )

NIBBLE - 4 bits

KB --> MB --> GB--> TB --> PB --> EB --> ZB

1KB - 1024 Bytes.