1. A frame-based computer system implemented on a hand-held pen-based device, said computer system comprising: computation means; memory means coupled to said computation means; input means implemented by a view system of said frame-based computer system, said input means coupled to said computation means; output means implemented by said view system of said frame-based computer system, said output means coupled to said computation means; a frame system stored in said memory means and implemented on said computation means for providing a data structure for said frame-based computer system, said frame system including frame objects, where each frame object is a logical software unit within said computer system having both data and processes which give said frame object attributes and capabilities, said frame system also including function frames arranged to contain a representation of an expression in a scripting language capable of implementing a computer process and arranged to be associated with a frame object, said frame system operable to implement the execution of input or output scripts contained within said function frames; means for detecting an output request initiated by said frame-based computer system and for causing a frame object of said frame system to determine an associated output function frame in order to implement an output script comprising a sequence of computer-implemented process steps which causes said output means to make an output through said view system; and means for detecting an input initiated by an external device or user from said input means and for causing a frame object of said frame system to determine an associated input function frame in order to implement an input script comprising a sequence of computer-implemented process steps which causes an input into said frame system by way of said view system.