1. In operation of a programmable computer the method which comprises: (a) storing in a first register the address of a first element of a set of dedicated workspace elements in main memory; (b) storing in a second register the memory address of a current instruction; (c) maintaining in a third register the current status of execution of the program of which said instruction forms a part; (d) utilizing as problem program workspace said set of workspace elements; (e) upon occurrence of an interrupt transferring the contents of said first register into a temporary store; (f) entering into said first register the address of a first element of a second set of dedicated workspace elements; and (g) storing the contents of said temporary store and of said second and third registers in elements of said second set.