APG Consultancy LTD

Data Storage

Storage on a PC is normally measured in Megabytes (MB), Gigabytes (GB) and Terabytes (TB). These values are normally based on multiples of 1000, but in computer terms they are typically stated as multiples of 1024, see the following table:

Binary / Computing

1 Byte = 8 Bits = A single character

1 KB = 1024 Bytes

1 MB = 1024 KBytes = 1,048,576 Bytes

1 GB = 1024 MB = 1,073,741,824 Bytes

1 TB = 1024 GB = 1,099,511,627,776 Bytes

Decimal (IEC)

1 Byte = 8 Bits = A single character

1 KB = 1000 Bytes

1 MB = 1000 Kbytes = 1,000,000 Bytes

1 GB = 1000 MB = 1,000,000,000 Bytes

1 TB = 1000 GB = 1,000,000,000,000 Bytes

Music Tracks

Photos

Movies

128 GB

32,000

25,000

32

512 GB

125,000

100,000

125

1 TB

250,000

200,000

250

1 Song (MP3 or AAC) is around 4 megabytes in size.
1 Photo is around 5 megabytes (Varies considerably depending on number of megapixels/quality).
1 Movie is around 4 gigabytes (depends on movie length, resolution and encoding quality).
Games vary considerably in size. Smaller games such as solitaire may be a few megabytes in size, larger games such as World or Warcraft may be tens of gigabytes in size

The table below lists common types of storage:

Hard Disk Drive (HDD)

Normally housed within a computer, can also be placed in an external enclosure and connected external via USB/Thunderbolt. Uses a spinning magnetic disk and is read/written to using a magnetic head which has to move across the surface of the disk. Typical speeds are around 80 megabytes per second. The main disadvantage is spin-up speed (it takes seconds to get the disk spinning) and access time (it takes a while to move the heads to where the required data is located). Advantage is cost, a 4TB drive can be around £100.

Solid State Disk (SSD)

A replacement for the hard disk drive which uses memory devices instead of a spinning disk. Advantages are much higher speed (100s of megabytes per second), virtually zero startup and access times. Much more expensive than a spinning hard drive, a 1TB drive is around £100.

Flash

Similar to a Solid State Drive, used for storing permanent data on a number of devices such as phones/cameras/computers. Does not lose its contents when power is removed.

USB Stick

Plugs directly into a USB connector, normally very small. Cheap versions can be very slow, moving data at a few megabytes per second, professional/expensive versions can be very fast reading/writing 100s of megabytes per seconds.

RAM

RAM is memory which is used on a computer/device to hold data/software which is currently being used, such as a document which is being displayed/edited and the software being used to perform the editing. The contents of RAM is lost when power is removed.