3686	JUMP	EXX		Go to the next alternate register set.
3687	JUMP-2	LD	E,(HL)	The next literal (jump length) is
				put in the E' register.
		LD	A,E	The number 00 hex or FF hex
		RLA		is formed in A according as E'
		SBC	A,A	is positive or negative, and is
		LD	D,A	then copied to D'.
		ADD	HL,DE	The registers H' & L' now hold
		EXX		the next literal pointer.
		RET		Finished.

THE 'JUMP ON TRUE' SUBROUTINE
(Offset 00: 'jump-true')

This subroutine executes a conditional jump if the 'last value' on the calculator stack, or more precisely the number addressed currently by the DE register pair, is true.

368F	jump-true	INC	DE	Point to the third byte, which is
		INC	DE	zero or one.
		LD	A,(DE)	Collect this byte in the A
				register.
		DEC	DE	Point to the first byte once
		DEC	DE	again.
		AND	A	Test the third byte: is it zero?
		JR	NZ,3686,JUMP	Make the jump if the byte is
				non-zero, i.e. if the number is
				not-false.
		EXX		Go to the alternate register set.
		INC	HL	Pass over the jump length.
		EXX		Back to the main set of
				registers.
		RET		Finished.

THE 'END-CALC' SUBROUTINE
(Offset 38: 'end-calc')

This subroutine ends a RST 0028 operation.

369B	end-calc	POP	AF	The return address to the
				calculator ('RE-ENTRY') is
				discarded.
		EXX		Instead, the address in H'L' is
		EX	(SP).HL	put on the machine stack and
		EXX		an indirect jump is made to it.
				H'L' will now hold any earlier
				address in the calculator chain
				of addresses.
		RET		Finished.

THE 'MODULUS' SUBROUTINE
(Offset 32: 'n-mod-m')

This subroutine calculates M (mod M), where M is a positive integer held at the top of the calculator stack, the 'last value', and N is the integer held on the stack beneath M.
The subroutine returns the integer quotient INT (N/M) at the top of the calculator stack, the 'last value', and the remainder N-INT (N/M) in the second place on the stack.
This subroutine is called during the calculation of a random number to reduce N mod 65537 decimal.

36A0	n-mod-m	RST	0028,FP-CALC	N,M
		DEFB	+C0,st-mem-0	N,M	mem-0 holds M
		DEFB	+02,delete	N
		DEFB	+31,duplicate	N, N
		DEFB	+E0,get-mem-0	N, N, M
		DEFB	+05,division	N, N/M
		DEFB	+27,int	N, INT (N/M)