Master–slave (technology)

In engineering, master–slave is a relationship between two systems in which one controls the other. In some cases, one master controls just one slave system, but in others, there are multiple slave systems controlled by the same master. Sometimes the master is a different kind of system than the slave, but sometimes there are multiple similar systems and one of them is designated the master in order to centralize external (i.e., user) control of the collection. It is also used to distinguish between systems that only issue commands (master) and those that only accept commands (slave).

Due to its association with slavery, the terminology is a subject of controversy and has been replaced with alternative terms in some cases.