•Kilobyte:-1KB = 1024 byte.
• Bit :• The amount of storage space needed to hold either 1 or 0
• Bit -> Binary Digit .
• Smallest unit of computer memory.
• Byte:• Byte = 8 bits .
• The amount of storage space needed to hold 1 character.
• Kilobyte:• 1KB = 1024 byte.
• Megabyte:• 1MB = 1024 KB.
• Gigabyte:• 1GB = 1024 MB.
• Terabyte:• 1Terabyte = 1024 GB.
•Kilobyte:-1KB = 1024 byte.
• H.D.D :• Hard Disk Drive.
• Information is saved to the H.D.D ,remains there to be
retrieved.
• Capacity -> ( Gigabytes ).
• Access time : is the time required by the H.D.D to search for ,
identify or process data stored on it.
• Access time is measured in millisecond
• Large capacity tend to have faster access time. ( α )
• The large capacity & faster access time -> high cost (α )
• F.D.D :• Floppy Disk Drive (Portable Disks).
• Uses floppy disks to store information ( data ).
• Most common type of floppy disks is 3½ " .
• Capacity : 1.44 MB.
• Cost : low cost .
•Kilobyte:-1KB = 1024 byte.
• Zip Drive :• Offered the portability of floppy disk , combined with either
(100 MB) or (200 MB) capacity .
• Use Special Zip Disks
• Similar to floppy in appearance but larger and heavier.
• More expensive.
• H.D , F.D , Zip Disks :• constructed from thin disks of non-metallic materials with
a coating Of magnetic medium, This allow data to be
saved as magnetic dots on either surfaces.
• These dots are arranged in circles called tracks each of
which subdivided into sectors.
• The process of creating these areas called formatting (as
new).
• DVD :• DVD -> Digital Versatile Disk . ( Digital video disk ).
• Capacity : more than 4 GB.
• Stores audio , video , games , ………
•Kilobyte:-1KB = 1024 byte.
• CD-ROM :• Use Compact Disk to read information on it (Read Only
Memory).
• Information can only be accessed , not modified .
• Capacity : up to 700 MB.
• Stores data that doesn’t need frequent updating (Programs).
• Low cost with large capacity.
• CD-R : Recordable , data can be saved only once .
• CD-RW : Rewritable , data can be saved more than once .
•Kilobyte:-1KB = 1024 byte.
• RAM :• Main Memory
• Ram -> ( Random Access Memory ) OR ( Read And Write
Memory ) .
• Temporary Memory.
• Contains S/W currently in use by computer .
• Can be modified .
• Volatile
• Data lost when the PC switched off or the electricity off.
• ROM :• Secondary Memory
• Rom -> ( Read Only Memory ).
• Permanent memory.
• Contains Machine startup S/W.
• Can't be modified or manipulated .
• Non-volatile.
• Data remains after the computer is switched off.
•Kilobyte:-1KB = 1024 byte.
• Characters:
• used to build up meaningful words, numbers and pictures
• File:
• Collection of text, numbers and graphics can be saved
with a name referred to as a file.
• Can contain different amount of data in many different
forms.
• The number of characters contained within each file will
determine the amount of memory needed to save it.
• See table in the book page 24
• In some data files characters can be organized within the
file into units (Records , Fields)
•Kilobyte:-1KB = 1024 byte.
• Record:
• Would contain all information for one person.
• Within each record there would be many fields.
• Field:
• Single piece of information.
• Each field as name, age , date of birth …
• File -> Records
• Record -> Fields
• File containing more than one record requires more
memory than file containing one record.
•Kilobyte:-1KB = 1024 byte.
• user can judge the performance of a pc according to How
quickly tasks are performed .
• There are no. of factors that determine the operating speed of a
PC:• Clock speed of the CPU.
• Capacity of RAM.
• Capacity and speed of H.D.D .
• No. of applications running.
( factors depend on nature and no. of tasks being performed )
•Kilobyte:-1KB = 1024 byte.
Calculations Depends on CPU speed.
Internet Depends on the Modem speed.
Data Depends on ( access time of H.D.D & RAM Size).