CALL	15E6,INPUT-AD	The signal is now accepted, like
				a 'key-value'.
		LD	BC,+0000	The default length of the
				resulting string is zero.
		JR	NC,365F,R-I-STORE	Jump if there was no signal.
		INC	C	Set the length to 1 now.
		RST	0030,BC-SPACES	Make a space in the work space.
		LD	(DE),A	Put the string into it.
365F	R-I-STORE	CALL	2AB2,STK-STO-$	Pass the parameters of the string
				to the calculator stack.
		POP	HL	Restore CURCHL and the
		CALL	1615,CHAN-FLAG	appropriate flags.
		JP	35BF,STK-PNTRS	Exit, setting the pointers.

THE 'CODE' FUNCTION
(Offset 1C: 'code')

This subroutine handles the function CODE A$ and returns the Spectrum code of the first character in A$, or zero if A$ should be null.

3669	code	CALL	2BF1,STK-FETCH	The parameters of the string are
				fetched.
		LD	A,B	The length is tested and the A
		OR	C	register holding zero is carried
		JR	Z,3671,STK-CODE	forward is A$ is a null string.
		LD	A,(DE)	The code of the first character is
				put into A otherwise.
3671	STK-CODE	JP	2D28,STACK-A	The subroutine exits via
				STACK-A which gives the
				correct 'last value'.

THE 'LEN' FUNCTION
(Offset 1E: 'len')

This subroutine handles the function LEN A$ and returns a 'last value' that is equal to the legnth of the string.

3674	len	CALL	2BF1,STK-FETCH	The parameters of the string are
				fetched.
		JP	2D2B,STACK-BC	The subroutine exits via
				STACK-BC which gives the
				correct 'last value'.

THE 'DECREASE THE COUNTER' SUBROUTINE
(Offset 35: 'dec-jr-nz')

This subroutine is only called by the SERIES GENERATOR subroutine and in effect is a 'DJNZ' operation but the counter is the system variable, BREG, rather than the B register.

367A	dec-jr-nz	EXX		Go to the alternative register set
		PUSH	HL	and save the next literal pointer
				on the machine stack.
		LD	HL,+5C67	Make HL point to BREG.
		DEC	(HL)	Decreae BREG.
		POP	HL	Restore the next literal pointer.
		JR	NZ,3687,JUMP-2	The jump is made on non-zero.
		INC	HL	The next literal is passed over.
		EXX		Return to the main register set.
		RET		Finished.

THE 'JUMP' SUBROUTINE
(Offset 33: 'jump')

This subroutine executes an unconditional jump when called by the literal '33'. It is also used by the subroutines DECREASE THE COUNTER and JUMP ON TRUE.