A dual instruction set processor can decode and execute both code received from a network and other code supplied from a local memory. Thus, the dual instruction set processor is capable of executing two different types of instructions, from two different sources, permitting the dual instruction set processor to have maximum efficiency. A computer system with the foregoing described dual instruction set processor, a local memory, and a communication interface device, such as a modem, for connection to a network, such as the Internet or an intranet, can be optimized to execute, for example, JAVA code from the network, and to execute non-JAVA code stored locally, or on the network but in a trusted environment or an authorized environment.