Description:	A simple program to add two 4-bit numbers together and display the 5-bit sum.
Input:	Two 4-bit values from tape.
Output:	The 5-bit sum is displayed on the output lamps.
Written by:	bhilpert (2006 Sep)
Assembled:	Ref Tape Assembly --- -------- -------------------------------------------------- 000: 18.0D.00 CR1 IR1 13 / load first operand 001: 02.00.01 SR1 IR2 ^ / save high bits as well 002: 19.05.00 CR2 IR1 5 / load second operand 003: 03.00.01 SR2 IR2 ^ / save high bits as well 004: 1B.00.00 CR4 IR ADD / add low bits, no carry-in 005: 0D.00.0C OR1 CR5 / display low bits 006: 08.00.02 CR1 SR1 / retrieve upper bits 007: 09.00.03 CR2 SR2 / of both operands 008: 1B.08.00 CR4 IR ADC / add upper bits, with carry-in 009: 0E.00.0C OR2 CR5 / display high bits 010: 18.00.00 CR1 IR1 0 / clear CR1 011: 19.00.00 CR2 IR1 0 / clear CR2 012: 1B.08.00 CR4 IR ADC / add 0+0+carry 013: 0F.00.0C OR3 CR5 / display 5th bit of result