The EDSAC was the first truly operational computer and certainly has a "reduced" instruction set; really, it is an accumulator-based ISA, not a load-store GPR as we associate with the term. In the early days the deep significance of the 'stored program computer' was that the instructions were simply numbers stored in memory, which could therefore be operated on. However, this conceptual power obscured the practical importance of certain simple aspects of the instruction set that could eliminate the need for self-modifying code. It eventually disappeared for performance reasons - programming clarity motivations came later.
.a Write a simple (closed) subroutine sum(A,n) to sum an array of n integers and return the result un EDSAC using the "initial orders -- second form" described in the paper. Also show the snipet of code to call it and access the result.
.b. Write a recursive subroutine fact(n) that computes the factorial function.