1. In a speech recognizer for multiple contexts and a plurality of users, an instantaneous context switching system, comprising: a memory coupled to a data processing means, a speech input means coupled to the plurality of users for speech recognition purposes and an output character string utilization device; a first context partition in said memory including a first plurality of words, each said first plurality of words including a second plurality of phonemes; a second context partition in said memory including a third plurality of words, each said third plurality of words including a fourth plurality of phonemes; a pattern matching partition in said memory including a fifth plurality of phoneme pattern matching data units for sharing by both contexts; a first pointer map including a second plurality of pointers, each respective one of said second plurality of phonemes related to a respective one of said of fifth pattern matching data units; a second pointer map including a fourth plurality of pointers, each respective one of said fourth plurality of phonemes related to a respective one of said fifth plurality of pattern matching data units; and selection means coupled to said memory either for selecting said first context partition and said first pointer map or alternately for selecting said second context partition and said second pointer map, for converting speech input information received from said speech input means into character string information output to said character string utilization device using the shared phoneme pattern matching data units for both contexts; whereby, a context of a speech recognition application can be instantaneously changed without loading new pattern matching data units in said memory.