Department of Computer Application- COMPUTER Memory and Storage Devices PRIMARY MEMORY RAM AND ROM RAM: random access memory DRAM: dynamic RAM SDRAM (Synchronous DRAM) PROM: programmable ROM EEPROM: electronically EPROM

1. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Affiliated Institution of G.G.S.IP.U, Delhi
BBA(Gen)
Computer Fundamentals
(17107)
Bharti Dewani
Assistant Professor,IT

2. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
COMPUTER
Memory and Storage Devices

3. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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.

4. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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

5. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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)

6. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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.

7. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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

8. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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

9. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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.

10. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Magnetic Storage
As the medium
rotates, the head
writes the data

11. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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.

12. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Formatted Diskette

13. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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

14. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Hard Disk
• A read/write head travels across a spinning magnetic disk,
retrieving or recording data

15. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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).

16. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Optical Disk
0

17. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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)

18. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 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: