Computer Memory and Storage Devices

TRINITY INSTITUTE OF PROFESSIONAL STUDIES

Sector – 9, Dwarka Institutional Area, New Delhi-75Affiliated Institution of G.G.S.IP.U, Delhi

BBA(Gen)Computer Fundamentals

(17107)

Bharti DewaniAssistant Professor,IT

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

COMPUTER

Memory and Storage Devices

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

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.

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

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

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

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)

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Secondary Storage Devices

• Storage devices hold data, even when the computer is turned off.

• The physical material that actually holds data is called a storage medium. The surface of a floppy disk is a storage medium.

• The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device.

• The two primary storage technologies are magnetic and optical.

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Magnetic Storage Devices• Diskettes (floppy disks) (FDD)

• Hard disks (HD)

• High-capacity floppy disks (ZIP Disk)

• USB flash drive

• Magnetic tape

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Optical Storage Devices

• Compact Disk Read-Only Memory (CD-ROM)

• Digital Video Disk Read-Only Memory (DVD-ROM)

• CD-Recordable (CD-R)

• CD-Rewritable (CD-RW)

• PhotoCD

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Magnetic Storage Devices

• How Magnetic Storage Works A magnetic disk's medium contains iron particles, which can be polarized—given a magnetic charge—in one of two directions (north or south).

• Each particle's direction represents a 1 (on) or 0 (off), representing each bit of data that the CPU can recognize.

• A disk drive uses read/write heads containing electromagnets to create magnetic charges on the medium.

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Magnetic Storage

As the mediumrotates, the headwrites the data

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Magnetic Storage Devices - Diskettes

• Diskette drives, also known as floppy disk drives, read and write to diskettes (called floppy disks or floppies).

• In disks the areas to save data are organized as a set of concentric circles called Tracks. Floppy disks have 80 tracks. The disks are further divided into pie-slice Sectors.

• 300 rpm

• Diskettes size: 3.5-inch.

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Formatted Diskette

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Hard Disk Drive

• Purpose:– Long-term, nonvolatile storage– Large, inexpensive, slow level in the storage hierarchy

• Disk composition– A magnetic disk consist of a collection of platters (1to 20

per disk) that rotate on a spindle. – Disk surface divided into tracks (1000 to 4800 per platter).– Tracks are divided into sectors (64 per track), which are

the smallest unit that can be read or written.• Up to 10,000 rpm

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Hard Disk

• A read/write head travels across a spinning magnetic disk, retrieving or recording data

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Optical Storage Devices

• How Optical Storage Works An optical disk is a high-capacity storage medium. An optical drive uses reflected light to read data.

• To store data, the disk's metal surface is covered with tiny dents (pits) and flat spots (lands), which cause light to be reflected differently.

• When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on).

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Optical Disk

0

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Optical storage devices

• CD-ROM: compact disc ROM (Read Only Memory)– Capacity: 650MB

• CD-R: compact disc recordable• CD-RW: compact disc rewritable• DVD: digital versatile disc

– Capacity: 4.7GB – 17GB• DVD-R• DVD-RW (2 versions: + (plus) and – (dash)

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

DVD (Digital Versatile Disk)– Allows up to 17 gigabytes of storage (from 4.7 GB to 17

GB).– Compatible with older CD-ROM technology.– The four versions of the DVD: