Memory

What is Memory?

It facilitates the remembrance power to computer system.It refers to the physical devices used to store programs (sequences of instructions) or data (e.g. program state information) on a temporary or permanent basis for use in a computer or other digital electronic device. 

Primary Memory:

The term primary memory is used for the information in physical systems which are fast. (i.e. RAM), as a distinction from secondary memory, which are physical devices for program and data storage which are slow to access but offer higher memory capacity. Primary memory stored on secondary memory is called virtual memory. 

Primary Memory are two types:

1. Volatile Memory
2. Non-Volatile Memory

Volatile Memory:

Volatile memory is computer memory that requires power to maintain the stored information. Most modern semiconductor volatile memory is either Static RAM or dynamic RAM. 

SRAM:

SRAM retains its contents as long as the power is connected and is easy to interface to but uses six transistors per bit. 

DRAM:

Dynamic RAM is more complicated to interface to and control and needs regular refresh cycles to prevent its contents being lost. However, DRAM uses only one transistor and a capacitor per bit, allowing it to reach much higher densities and, with more bits on a memory chip, be much cheaper per bit. SRAM is not worthwhile for desktop system memory, where DRAM dominates, but is used for their cache memories.. 

Non-Volatile Memory:

Non-volatile memory is computer memory that can retain the stored information even when not powered. 

Examples: Non-Volatile memory are flash memory and ROM/PROM/EPROM/EEPROM memory (used for firmware such as boot programs). 

Cache Memory:

Cache memory is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM. As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data from larger memory. It is of two types- L1 cache is on the same chip as the microprocessor. L2 is usually a separate static RAM (SRAM) chip.

Secondary Memory: 

• Hard Disk (Local Disk)
• Pen Drive
• Floppy Disks
• Memory Cards
• External Hard Disk
• Blu ray Disk

Blu ray Disk:

Blu-ray (not Blue-ray) also known as Blu-ray Disc (BD), is the name of a new optical disc format. The format offers more than five times the storage capacity of traditional DVDs and can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. While current optical disc technologies such as DVD, DVD±R, DVD±RW, and DVD-RAM rely on a red laser to read and write data, the new format uses a blue-violet laser instead, hence the name Blu-ray. 

Unit of Memory:

The smallest unit is bit, which mean either 0 or 1

1 Bit                 = 0 or 1 

1 Byte              = 8 Bit

1 Nibble           = 4 Bit

1 Kilo Byte       = 1024Byte

1 Mege Byte    = 1024 KB

1 Gega Byte    = 1024 MB

1 Tera Byte      = 1024 GB

1 Peta Byte      = 1024 TB

1 Exa Byte       = 1024 PB

1 Zetta Byte     = 1024 EB

1 Yotta Byte     = 1024 YB