Online Computer Terms Dictionary - D

differential backup

<operating system> A kind of backup that copies all files that have changed since the last full backup. Each differential backup will include all files in previous differential backups since the full backup so to restore a version of a file, you only need to search the full backup and the relevant differential backup.

Some systems support differential backup by associating an "Archive" flag with each file and setting this flag whenever the file is modified to indicate that it should be included in the next backup. A differential backup does not change this flag, whereas an incremental backup resets it.

(2004-03-05)

differential driver

<hardware> An electronic device (commonly an integrated circuit), containing two amplifiers, used to drive a differential line.

(1995-03-14)

differential line

<hardware> A kind of electrical connection using two wires, one of which carries the normal signal (V) and the other carries an inverted version the signal (-V). A differential amplifier at the receiver subtracts the inverted signal from the normal signal to yield a signal proportional to V. This subtraction is intended to cancel out any noise induced in the wires, on the assmption that the same level of noise will have been induced in both wires. Twisted pair wiring is often used to try to ensure that this is the case.

The two wires might be connected at the receiver to separate analogue to digital converters and the subtraction performed digitally.

The RS-422 serial line standard specifies differential drivers and receivers, whereas the earlier RS-232 standard does not.

Opposite: single ended.

(1995-03-08)