Spectrum ROM: Routine at 13855

13855: THE 'STR$' FUNCTION (offset 46)

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	13855	LD BC,1	One space is made in the work space and its address is copied to K-CUR, the address of the cursor.
	13858	RST 48
	13859	LD (23643),HL
	13862	PUSH HL	This address is saved on the stack too.
	13863	LD HL,(23633)	The current channel address (CURCHL) is saved on the machine stack.
	13866	PUSH HL
	13867	LD A,255	Channel 'R' is opened, allowing the string to be 'printed' out into the work space.
	13869	CALL CHAN_OPEN
	13872	CALL PRINT_FP	The 'last value', X, is now printed out in the work space and the work space is expanded with each character.
	13875	POP HL	Restore CURCHL to HL and restore the flags that are appropriate to it.
	13876	CALL CHAN_FLAG
	13879	POP DE	Restore the start address of the string.
	13880	LD HL,(23643)	Now the cursor address is one past the end of the string and hence the difference is the length.
	13883	AND A
	13884	SBC HL,DE
	13886	LD B,H	Transfer the length to BC.
	13887	LD C,L	Transfer the length to BC.
	13888	CALL STK_STO	Pass the parameters of the new string to the calculator stack.
	13891	EX DE,HL	Reset the pointers.
	13892	RET	Finished.
Note: see PRINT_FP for an explanation of the 'PRINT "A"+STR$ 0.1' error.