In addition to its numerical representation, digital data has a physical representation. For example, the bits in a hard disk are magnetic impulses on platters that can be read with analog sensors. Network wires contain electric signals that represent network packets and keyboard cables contain electric signals that represent which keys were pressed. A computer converts the electric signals to a digital representation. Digital photography and video are a digital representation of the light associated with physical objects. Digital data can be stored on many mediums and each has different properties that determine how long the data will reside. For example, data will reside on a keyboard.
