Spectrum ROM: Routine at 361F

361F: THE 'STR$' FUNCTION (offset +2E)

The address of this routine is found in the table of addresses. It is called indirectly via fp_calc_2. This subroutine handles the function STR$ X and returns a 'last value' which is a set of parameters that define a string containing what would appear on the screen if X were displayed by a PRINT command.
str	361F	LD BC,$0001	One space is made in the work space and its address is copied to K-CUR, the address of the cursor.
	3622	RST $30
	3623	LD ($5C5B),HL
	3626	PUSH HL	This address is saved on the stack too.
	3627	LD HL,($5C51)	The current channel address (CURCHL) is saved on the machine stack.
	362A	PUSH HL
	362B	LD A,$FF	Channel 'R' is opened, allowing the string to be 'printed' out into the work space.
	362D	CALL CHAN_OPEN
	3630	CALL PRINT_FP	The 'last value', X, is now printed out in the work space and the work space is expanded with each character.
	3633	POP HL	Restore CURCHL to HL and restore the flags that are appropriate to it.
	3634	CALL CHAN_FLAG
	3637	POP DE	Restore the start address of the string.
	3638	LD HL,($5C5B)	Now the cursor address is one past the end of the string and hence the difference is the length.
	363B	AND A
	363C	SBC HL,DE
	363E	LD B,H	Transfer the length to BC.
	363F	LD C,L	Transfer the length to BC.
	3640	CALL STK_STO	Pass the parameters of the new string to the calculator stack.
	3643	EX DE,HL	Reset the pointers.
	3644	RET	Finished.
Note: see PRINT_FP for an explanation of the 'PRINT "A"+STR$ 0.1' error.