CCF		Complement the carry flag.
		RET	NC	Return if not a valid character
				code.
		CP	+7B	Test against 7B hex, 1 more
				than the code for 'z'.
		RET		Finished.

THE 'DECIMAL TO FLOATING POINT' SUBROUTINE
As part of syntax checking decimal numbers that occur in a BASIC line are converted to their floating-point forms. This subroutine reads the decimal number digit by digit and gives its result as a 'last value' on the calculator stack. But first it deals with the alternative notation BIN, which introduces a sequence of 0's and 1's giving the binary representation of the required number.

2C9B	DEC-TO-FP	CP	+C4	Is the character a 'BIN'?
		JR 	NZ,2CB8,NOT-BIN	Jump if it is not 'BIN'.
		LD	DE,+0000	Initialise result to zero in DE.
2CA2	BIN-DIGIT	RST	0020,NEXT-CHAR	Get the next character.
		SUB	+31	Subtract the character code for
				'1'.
		ADC	A,+00	0 now gives 0 with carry set; 1
				gives 0 with carry reset.
		JR	NZ,2CB3,BIN-END	Any other character causes a
				jump to BIN-END and will be
				checked for syntax during or
				after scanning.
		EX	DE,HL	Result so far to HL now.
		CCF		Complement the carry flag.
		ADC	HL,HL	Shift the result left, with the
				carry going to bit 0.
		JP	C,31AD,REPORT-6	Report overflow if more than
				65535.
		EX	DE,HL	Return the result so far to DE.
		JR	2CA2,BIN-DIGIT	Jump back for next 0 or 1.
2CB3	BIN-END	LD	B,D	Copy result to BC for stacking.
		LD	C,E	
		JP	2D2B,STACK-BC	Jump forward to stack the
				result.

For other numbers, first any integer part is converted;	if the next character is a decimal, then the decimal fraction is considered.

2CB8	NOT-BIN	CP	+2E	Is the first character a '.'?
		JR	Z,2CCB,DECIMAL	If so, jump forward.
		CALL	2D3B,INT-TO-FP	Otherwise, form a 'last value' of
				the integer.
		CP	+2E	Is the next character a '.'?
		JR	NZ,2CEB,E-F0RMAT	Jump forward to see if it is an 'E'.
		RST	0020,NEXT-CHAR	Get the next character.
		CALL	2D1B,NUMERIC	Is it a digit?
		JR	C,2CEB,E-FORMAT	Jump if not (e.g. 1.E4 is allowed).
		JR	2CD5,DEC-STO-1	Jump forward to deal with the
				digits after the decimal point.
2CCB	DECIMAL	RST	0020,NEXT-CHAR	If the number started with a
		CALL	2D1B,NUMERIC	decimal, see if the next
				character is a digit.
2CCF	DEC-RPT-C	JP	C,1C8A,REPORT-C	Report the error if it is not.
		RST	0028,FP-CALC	Use the calculator to stack zero
		DEFB	+AO,stk-zero	as the integer part of such
		DEFB	+38,end-calc	numbers.
2CD5	DEC-STO-1	RST	0028,FP-CALC	Use the calculator again.
		DEFB	+A1,stk-one	Find the floating-point form of
		DEFB	+C0,st-mem-0	the decimal number '1', and