Storing Data
Abdul Wajid

1
Storage of Data
Instructions and data are held in main memory
which is divided into millions of addressable
storage units...
Bits
Computers use electronic circuits to
perform the tasks they are
programmed to complete.
These circuits can be in on...
Memory Sizes measurement
I nibble
= 4 bits
I byte
= 8 bits
I kilobytes (kb)
= 1024 bytes
1 Megabytes (Mb) = 1024kiloby...
Memory ( Main store)
 Memory is the name given to the group of chips inside
the processing unit
 The data held in the me...
RAM & ROM
Ram

ROM
Its temporary memory Its Permanent memory
Read and Write data It can only be read
Data can be chan...
Semiconductor

Volatile

Memory
types
Non-volatile

RAM

SRAM

ROM

DRAM

PROM

EPROM

7
PROM & EPROM
PROM
 Programmable read only
memory
 User can write instruction
only one time
 Instructions can not be
era...
SRAM & DRAM
SRAM
Static Random Access
Memory
It can store its value
without any need to
refresh the data as
long as the ...
Floppy Disk
Used to transfer small amount of data between
computers
Come with 3.5 inch disk drive
Floppy disk is the ha...
Hard drives
 Consist a several disks on a single
spindle
 Each disk surface able to store data
 Each surface can have i...
Hard Disk Mechanism

12
Magnetic Tape
Large spools of tape are used very large
computer systems that need to hold huge
amount of data
They are n...
CD-ROM Drives
Use the same technology as music CD and CD
players
The data is stored on the disk digitally and a
laser be...
CD-R
A CD recordable (CD-R) drive has a
read/write capability.
Using this device you can write around 15
minutes
CD-R c...
Digital Versatile Disks (DVD)
 Are similar to CD-ROMs in that they look identical and
are used to store lots of date.
 L...
Backup devices
It is important to take regular backups of both
data and programs for security purposes.
Floppy disks do ...
Tape streamers
Are devices used to backup the data contained
on hard drives

Zip Drives
Are useful for backing up hard d...
Jaz Drives
Is a removable disk drive which is very
fast at transferring data.
Each disk hold up to 2 GB of data
The hig...
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Storing data ch 4

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Storing data ch 4

  1. 1. Storing Data Abdul Wajid 1
  2. 2. Storage of Data Instructions and data are held in main memory which is divided into millions of addressable storage units called bytes. One byte can hold one character One byte can hold 8 bits Computers work by using pulses of voltage which represent either 1 or 0 A low voltage mean 0 and high voltage mean 1 Total bytes in main memory referred to as the computer’s memory size. 2
  3. 3. Bits Computers use electronic circuits to perform the tasks they are programmed to complete. These circuits can be in one of two states - ‘On’ or ‘Off’. 3
  4. 4. Memory Sizes measurement I nibble = 4 bits I byte = 8 bits I kilobytes (kb) = 1024 bytes 1 Megabytes (Mb) = 1024kilobytes 1 gigabytes (Gb) = 1024Megabytes 1 terabytes (TB) = 1024Gigabytes 4
  5. 5. Memory ( Main store)  Memory is the name given to the group of chips inside the processing unit  The data held in the memory is available to the computer Memory is used to hold following information  Programs  Input data  Working Area  Output data  There are two types of main memory  Ram (Random access memory )  ROM (Read only memory ) 5
  6. 6. RAM & ROM Ram ROM Its temporary memory Its Permanent memory Read and Write data It can only be read Data can be changed Data can not change or deleted or deleted It is a Volatile memory It is non Volatile The instructions are The instructions written into Rom at written in Ram at the manufacturing time. time of execution (BIOS) 6
  7. 7. Semiconductor Volatile Memory types Non-volatile RAM SRAM ROM DRAM PROM EPROM 7
  8. 8. PROM & EPROM PROM  Programmable read only memory  User can write instruction only one time  Instructions can not be erased  If there is error while writing on PROM ,it becomes unusable EPROM  Erasable programmable Rom  User can write instruction many times  Instructions can be erased  If there is error while writing on EPROM, it can still be used again 8
  9. 9. SRAM & DRAM SRAM Static Random Access Memory It can store its value without any need to refresh the data as long as the power is available It utilizes less power It is more expansive DRAM Dynamic Random Access Memory It has to be refreshed after each read operation. It utilizes more power It is less expansive 9
  10. 10. Floppy Disk Used to transfer small amount of data between computers Come with 3.5 inch disk drive Floppy disk is the hard case the disk inside in floppy Magnetic disk store binary data as a magnetic pattern on the disk surface It hold 1.44MB of data Before the data is stored on a disk the disk needs to be formatted 10
  11. 11. Hard drives  Consist a several disks on a single spindle  Each disk surface able to store data  Each surface can have its own read/write head  This enables the read/write heads to operate simultaneously which means that the data can be transferred more quickly than by using the large disk  Hard disk is available in all sorts of sizes  A typical computer will have a hard disk capacity of around 20 GB 11
  12. 12. Hard Disk Mechanism 12
  13. 13. Magnetic Tape Large spools of tape are used very large computer systems that need to hold huge amount of data They are not as common as they used to be They look similar to audio cassettes except they are larger Their main use is for making backup copies of hard disk 13
  14. 14. CD-ROM Drives Use the same technology as music CD and CD players The data is stored on the disk digitally and a laser beam is used to read the disk Light is used to read the disk the data may be packed closely and disk therefore has a huge capacity Are included in multimedia system CD-ROMs can be filled with clip art ,encyclopedia ,photograph and all sort of data Are read only disk A CD holds around 600MB data 14
  15. 15. CD-R A CD recordable (CD-R) drive has a read/write capability. Using this device you can write around 15 minutes CD-R can be used to back up hard drives. Standard CD-R disks can be written to only once but there is a type of disks can be written, erased and rewritten They are more expensive than CD-R disks 15
  16. 16. Digital Versatile Disks (DVD)  Are similar to CD-ROMs in that they look identical and are used to store lots of date.  Like CD-ROM they can be used to store computer application software, multimedia programs and full length movies  This is because CD-Rom typically store 650 MB of data whereas to a DVD stores between 4.7 GB  DVDs also are used to store movies where they produce much better quality pictures and sound compared to a normal video tape.  A film stored on DVD can even be made to offer the viewer a choice of several languages in which it can be played back 16
  17. 17. Backup devices It is important to take regular backups of both data and programs for security purposes. Floppy disks do not have a very high storage capacity and so are seldom used for backup. Instead higher capacity and faster storage devices are used and main ones are as follows Tape streamers Zip drives Jaz drives 17
  18. 18. Tape streamers Are devices used to backup the data contained on hard drives Zip Drives Are useful for backing up hard drives They are high storage capacity floppy disks which are slightly larger and twice as thick as normal floppies They can typical store data 100 MB or 250 MB 18
  19. 19. Jaz Drives Is a removable disk drive which is very fast at transferring data. Each disk hold up to 2 GB of data The higher data transfer rate means that they can be used to backup data in a very short time They can be used for everyday storage just like an ordinary disk drive 19

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