1. A computer system for executing a compressed stream of instructions, the stream of instructions stored in a program store, the instruction stream having literal instructions and one or more Echo instructions for repeating one or more literal instructions, each Echo instruction relating to one or more literal instructions located in the program store, the system comprising: an execution module that executes literal instructions in the instruction stream; an evaluation module that determines whether an instruction is a literal instruction or an Echo instruction; an Echo module for executing the one or more Echo instructions; and wherein at least one Echo instruction comprises: a first parameter that identifies the first instruction to be repeated; and a second parameter that identifies the last instruction to be repeated.