This document discusses different types of computer memory and storage devices. It describes the main memory units like RAM and ROM. RAM is volatile and used for temporary storage, while ROM is non-volatile and used for permanent storage. RAM types include SRAM and DRAM, and ROM types include PROM, EPROM, and EEPROM. Secondary storage devices like magnetic tapes, disks, optical disks are also covered, explaining their uses, types, and characteristics in 1-3 sentences each. Factors affecting processor speed and the instruction cycle are briefly mentioned.

1. by
K.Thamizhselvi
Assist Professor
Bon Secours College for Women, Thanjavur.

2. CPU-Central Processing Unit

3. MEMORY UNIT
• Internal storage area
• Also Known as ‘Primary or Main Memory’
• 2 operations
– Read: transfer information from memory to
other devices.
– Write: transfer information into memory
Types:
 RAM – Random Access Memory
 ROM – Read Only Memory

4. RAM – Random Access Memory
• Read and write memory
• Temporary Memory
• RAM is volatile ie when power is off data
will be lost.

5. Types of RAM
STATIC RAM
• the memory retains its
contents as long as power
is being supplied.
• Long life
• Faster
• Used as cache memory
• Large size
• Expensive
• High power consumption
DYNAMIC RAM
• DRAM must be
continually refreshed in order
to maintain the data.
• Short data lifetime
• Slower as compared to SRAM
• Used as RAM
• Smaller in size
• Less expensive
• Less power consumption

6. Types of DRAM
• Conventional DRAM
• FPM DRAM – Fast Page Mode
• EDO DRAM – Extended Data Out
• BEDO DRAM – Burst Extended Data Out
• SDRAM – Synchronous DRAM
• DDR DRAM – Double Data Rate
• DRDRAM – Direct Rambus
• SLDRAM – Synchronous Link

7. Advantages & Disadvantages of
Static RAM
Advantages
–Simplicity
–Speed
Disadvantages
–Cost
–Size

8. ROM – READ ONLY MEMORY
• The memory from which we can only read
but cannot write on it.
• Non-volatile in nature
• Permanent Memory
• Cheaper than RAMs

9. Types of ROM
• PROM – Programmable Read Only Memory
• EPROM – Erasable Programmable Read Only Memory
• EEPROM – Electrically Erasable Programmable Read
Only Memory
• FLASH MEMORY

10. Factors affecting processor speed
• Register – Word Length – 16/32 bits
• Memory – Swapping technique – copy
data to main memory
• Clock Speed – System clock range 2GHz
• Bus – Collection of wires connect all
internal components.
• Cache Memory – High speed storage
Device

11. Various instructions executed by the
processor – Instruction Set
2 types:
CISC – Complex Instruction Set Computing
RISC – Reduced Instruction Set Computing
 Execution of instruction takes series of
steps called Machine Cycle.
2 types:
Instruction Cycle – Fetch & Decode
Execution Cycle – Execute & Store

12. AUXILIARY (SECONDARY) STORAGE
DEVICES

13. • This type of memory is also known as external
memory or non-volatile or backup memory.
• Data is permanently stored even if power is
switched off.
• The contents of secondary memories are first
transferred to the main memory, and then the CPU
can access it.
• Computer may run without the secondary memory.
• For example disk, CD-ROM, DVD, etc.
Advantages:
Economy
Capacity
Security

14. MAGNETIC MEDIA
Magnetic tape Magnetic disk

15. MAGNETIC TAPES
• Have large storage capacities and used to
transport large amount of data.
• Sequential access
• Commonly used for backing-up data
• Types:
–Quarter inch Cartridge Tapes (QIC Tape)
–8mm Helical Scan Tapes
–DAT Cartridge (Digital Audio Tape)

16. MAGNETIC DISK
• Uses a magnetization process to write,
rewrite and access data.
• Random access
• Data can be accessed directly – Direct
Access Storage Devices.(DASD)
• Types:
–Solid / Hard Disk (Disk Pack, Winchester
disk etc.)
–Flexible Disk (Floppy disk, Zip Disk, Jaz
disk, Super disk Etc.)

17. HARD DISK
• Thin steel platters with iron oxide coating.
• Electromagnetic read/write heads are
mounted on Access arms.
• Data on concentric circles – Tracks.
• Access time has 4 factors,
– Seek time
– Head switching
– Rotational delay time
– Data transfer

18. Zip / Jaz Disks
• Similar to floppy disks
•They are removable
• Their platters are made of a hard material
• Can operate at higher speeds than floppies.
• Newer standards hold more data
• Most people have outgrown floppy disks

19. Optical Disk
• Data is read and written using laser.
• A laser is used to determine if a pit is present
or not.
• 3 types:
 CD – ROM
 WORM
 Erasable

20. Floppy Disks
• Floppy disks is a soft magnetic disk
•Slower in access and low storage
capacity
•Their capacity hasn’t increased much
• Many computers today do not even
come with floppy disk drives anymore.