AS Computing
Unit 1.6 Organisation of Data and File Access
What is a File?
A collection of related data
Consists of records
Treated as one unit by backing storage
Files are processed by applications
Storage
Primary Storage Secondary Storage
Accessed directly by the CPU Accessed indirectly by the CPU
Can be Volatile or Non-Volatile Always Non-Volatile
Faster Slower
Lower Storage Capacity Higher Storage Capacity
Types of Secondary Storage
Storage Media Portability Speed Capacity
Magnetic Tape Tape itself is very Slowest so it’s ideal Up to 5 Terabytes
good while the tape for archiving (5TB)
drive needed is quite
large
Floppy Disk Disc itself is very good Very slow to access Between 640
but the disk needs a and store data Kilobytes(kb) and 1.44
drive to be inserted Megabytes(Mb)
into
Hard Disk Bad because Hard Very fast compared to Ranges all over from
Disks are an internal the Floppy and Megabytes to
component in a PC Magnetic Disk Gigabytes to
Terabytes
Optical Disc (OD) Very Good OD: Faster than CD: About 650Mb
Compact Disc (CD) magnetic tape but DVD: Ranges from
Digital Versatile Disc slower than HDD or 4.7GB to 17GB
(DVD) Flash Memory
CD: Can transfer data
up to the speed of
7800KB/s or about 70
minutes of audio
DVD: Access rates of
600KB/s to 1.3MB/s
Flash Drive Very Good 30 to 100’s of MB/s 8 Megabytes to 512
Gigabytes
Flash Memory Card Very Good About 15MB/s 1GB to 16GB
Page |1 Luca Passariello AS Computing
Unit 1.6 Organisation of Data and File Access
What is a File?
A collection of related data
Consists of records
Treated as one unit by backing storage
Files are processed by applications
Storage
Primary Storage Secondary Storage
Accessed directly by the CPU Accessed indirectly by the CPU
Can be Volatile or Non-Volatile Always Non-Volatile
Faster Slower
Lower Storage Capacity Higher Storage Capacity
Types of Secondary Storage
Storage Media Portability Speed Capacity
Magnetic Tape Tape itself is very Slowest so it’s ideal Up to 5 Terabytes
good while the tape for archiving (5TB)
drive needed is quite
large
Floppy Disk Disc itself is very good Very slow to access Between 640
but the disk needs a and store data Kilobytes(kb) and 1.44
drive to be inserted Megabytes(Mb)
into
Hard Disk Bad because Hard Very fast compared to Ranges all over from
Disks are an internal the Floppy and Megabytes to
component in a PC Magnetic Disk Gigabytes to
Terabytes
Optical Disc (OD) Very Good OD: Faster than CD: About 650Mb
Compact Disc (CD) magnetic tape but DVD: Ranges from
Digital Versatile Disc slower than HDD or 4.7GB to 17GB
(DVD) Flash Memory
CD: Can transfer data
up to the speed of
7800KB/s or about 70
minutes of audio
DVD: Access rates of
600KB/s to 1.3MB/s
Flash Drive Very Good 30 to 100’s of MB/s 8 Megabytes to 512
Gigabytes
Flash Memory Card Very Good About 15MB/s 1GB to 16GB
Page |1 Luca Passariello AS Computing
