Computer Memory Full Notes PDF
o A memory computer has a storage part.
o It stores data, information, programs during processing in a computer.
o It stores the data temporarily or permanently. Memory was instrumental in saving and retrieving data.
Types of memory
Mainly computer has two types of memory
1. Primary Memory / Volatile Memory.
2. Secondary memory / non-volatile memory.
Primary Memory / Volatile Memory –
o Primary memory is the internal memory of the computer.
o It is also known as main memory and temporary memory.
o Primary memory holds the data and instruction the computer is currently working on.
o Primary memory is unstable by nature. This means that all data is lost when the power is turned off.
Primary Memory Type
Primary memory is usually of two types.
1. RAM (Random Access Memory) –
o This is for random access memory.
o RAM is known as memory read / write.
o It is usually refereed as the main memory of a computer system.
o It is a temporary memory.
o Information stored in this memory is lost because the power supply to the computer is off.
o This is why RAM is also called “volatile memory”
RAM-RAM types are also of two types:
a) Static RAM-
o Static RAM, also known as SRAM, maintains stored information as long as the power supply is on.
o SRAMs are of higher coast and consume more power.
o They have higher speed than dynamic RAM
B) Dynamic RAM-
O Dynamic RAM is also known as DRAM, its stored information in a very short time (a few milliseconds) even if the power supply is on.
o Dynamic RAMs are inexpensive and medium speed and also consume less power.
2. ROM (memory read-only) –
O Read for only memory.
o ROM is a permanent type of memory.
When the power supply is turned off, its contents are not lost.
o ROM content is fixed by the computer manufacturer and is stored permanently at the time of manufacturing.
The ROM cannot be overwritten by the computer. It is also called “non-volatile memory”.
There are three types of ROM memory names:
1. PROM (Programmable Read-Only Memory) –
The PROM chip is a programmable ROM.
o It is PROM chips for writing and reading multiple data at once.
o Once the chip is programmed, the recorded information cannot be changed.
O PROM is also nonvolatile memory.
2. EPROM (erasable programmable read-only memory) –
o The EPROM chip can be timed and re-programmed by erasing the information previously stored.
o Information stored in the EPROM exposing the chip to ultraviolet light for some time.
3. EEPROM (electrically erasable program read-only memory) –
o EEPROM is programmed and erased by special electric waves in milliseconds.
o A single byte of data or the entire contents of the device can be erased.
2. Secondary memory / Non-volatile memory – Secondary memory is the external memory of a computer. It is also known as auxiliary memory and permanent memory. It is used to permanently store various programs and information. Secondary memory is nature non-volatile. This means that data is stored permanently even when the power is turned off.
Secondary storage devices are:
1. Floppy Disk
2. Magnetic (hard) disk
3. Magnetic tape
4. Pen Drive
5. Winchester Disc