Memory Representation
Memory Representation
Memory Representation
Bit
Byte
Kilobyte
Megabyte
Gigabyte
Terabyte
RAM (Random Access Memory)
Hard Disk
Main Memory CPU
Types of RAM
SRAM (Static)
- volatile memory
- used as cache memory
DRAM (Dynamic)
- unstable
- needs refreshing
Difference between SRAM and DRAM
Data life
No. of chips
Speed
Cost
Heat production
Latency ROM (Read Only Memory)
Types
Masked ROM
Contains preprogrammed set of instructions
PROM
One-time programmable
EPROM
Erasable by ultraviolet light
EEPROM
Electrically erasable by applying small voltage
Flash ROM
Flash memory written in block sizes
Difference between ROM and
RAM
Volatility
Lifetime of contents
Cost
Storage capacity
Processing Speed
Programs?
RAM, ROM and CPU Interaction
1. Switch on ctr.
2. Loads data from ROM
3. Loads BIOS from ROM
4. Loads OS from hard disk into RAM.
5. Loads application into RAM.
6. After saving flush out the RAM.
Cache Memory
CPU Cache Memory Primary Memory Secondary Memory
Virtual Memory
It is a system memory that is simulated by the hard drive. When all the RAM is being used the computer will swap data to the hard drive and back to give the impression that there is slightly more memory.
Secondary Storage Devices
Magnetic Tapes
Magnetic Disk Optical Disk Magneto
Optical Disk
Floppy Disk
Hard Disk
Zip Disk
CD-ROM WORM
Sequential Access
Data
Data
Data
Data
Data
Data
Data
Data
Magnetic Tape
Plastic tape with magnetic coating
Magnetised and de-magnetised
Different sizes
Can be reused
Sequential access
Frames and tracks
Magnetic tape organization
Advantages
Non-volatile memory
High data recording density
Easily transportable
Disadvantages
Need dust free environment
Slow data access
Difficult to recover
Direct Access
Data
Data
Data
Data
Data
Data
Data
Data
Magnetic Disk
Plastic/metal circular plate/platter coated
with magnetic oxide layer.
1 and 0
Magnetised data converted into electrical pulses for reading and vice versa for writing
Reused
Reside in a protective case
Storage Organisation of magnetic disk
Tracks and sectors
Double-sided disks
Sector number, track number and surfacenumber
Cluster
Disk pack and Cylinder
Accessing data Seek, Rotate, Data transfer
Types of Magnetic disk
Floppy Disk
Hard Disk
Zip Disk
Advantages of Magnetic Disk
Direct access
Online and offline storage
Movable
Data transfer rate
High data recording densities
Disadvantages
Dust free environment
Costlier
Optical Disk
Advantages
Large capacity
Life span
Not affected by magnetic field
Portable
Disadvantages
Costlier
Needs both hardware and software forwriting
More complicated
Tips to choose good All-in-One printers suit to your work! The world's first computer data line associated card reader technology for pk 3ds Tablet pc or Mini netbook computer Challenge? Mike Ramsey Prevent Sweating Guide Review Is It Safe To Use A Baby Monitor? Best Computer Deals Online 3 Reasons to Use Stock Trade Programs to Double Your Investments Overnight Mammograms and Breast Implants How You can Get a Free Laptop The Best Slow Computer Fix for Doctors You want a Free Laptop Computer? Charming Bed and Breakfast Inns Can Recharge Your Batteries Where are the greatest projectors for computer systems?