.z80  	;use z80 mode
		;
		;*********************************************
		;* Small Example using STRU                  *
		;* by Rolf-Dieter Klein 821229 1.0           *
		;*********************************************

		; a small pocket calculator
		;
		;
	jp start 	;start main program
		;

	bdos equ 5 	;cp/m entry point

		; procedures for the calculator
		;



ci:		;get byte from console to akku
	push hl  	;save all registers
	push de
	push bc
	ld c,1  	;ci function
	call bdos
	pop bc
	pop de
	pop hl
	ret  	;result in akku


co:		;put byte to console
	push hl  	;value in c register
	push de
	push bc
	ld e,c  
	ld c,2
	call bdos
	pop bc
	pop de
	pop hl
	ret



		;
		;
print:		;print a string till 0
		;start adress at -> HL
;1 	while (hl)<>0
.L1:
	LD A,(hl)
	OR A
	JP Z,.L2
	ld c,(hl)
	call co
	inc hl
;1 	endwhile
	JP .L1
.L2:
	ret
		;
		;

getnum:		;get dezimal or hex number
		;$FF or 12333 are valid numbers
		;hl is result
		;carry means no value is valid
	ld a,0
	ld (flag),a 	;no sign  
	ld hl,0  	;initial value
	call ci  	;get first value
;1 	if a = '-' 	;negative sign
	CP  '-' 
	JP NZ,.L3
	ld a,1
	ld (flag),a
	call ci 	;get next
;1 	endif
.L3:
;1 	if a = '$' 	;is it a hex value ?
	CP  '$' 
	JP NZ,.L4
	call ci
;2 	if not a in ['0'..'9','A'..'F','a'..'f']
	CP '9'+1
	JR NC,.L6
	CP '0'+0
	JP NC,.L5
.L6:
	CP 'F'+1
	JR NC,.L7
	CP 'A'+0
	JP NC,.L5
.L7:
	CP 'f'+1
	JR NC,.L8
	CP 'a'+0
	JP NC,.L5
.L8:
	scf  	;error exit no hex number
;3 	exit
	RET
;2 	endif
.L5:
;2 	while a in ['0'..'9','A'..'F','a'..'f']
.L9:
	CP '9'+1
	JR NC,.L12
	CP '0'+0
	JP NC,.L11
.L12:
	CP 'F'+1
	JR NC,.L13
	CP 'A'+0
	JP NC,.L11
.L13:
	CP 'f'+1
	JR NC,.L14
	CP 'a'+0
	JP NC,.L11
.L14:
	JP .L10
.L11:
	add hl,hl 	;hl * 16
	add hl,hl
	add hl,hl
	add hl,hl
;3 	if a in ['A'..'F']
	CP 'F'+1
	JR NC,.L17
	CP 'A'+0
	JP NC,.L16
.L17:
	JP .L15
.L16:
	sub 'A'
	add a,10
;3 	else
	JP .L18
.L15:
;4 	if a in ['a'..'f']
	CP 'f'+1
	JR NC,.L21
	CP 'a'+0
	JP NC,.L20
.L21:
	JP .L19
.L20:
	sub 'a'
	add a,10
;4 	else
	JP .L22
.L19:
	sub '0'
;4 	endif
.L22:
;3 	endif
.L18:
	and 0fh
	ld e,a
	ld d,0
	add hl,de 	;result + new digit
	call ci  
;2 	endwhile
	JP .L9
.L10:
;1 	else
	JP .L23
.L4:
;2 	if not a in ['0'..'9']
	CP '9'+1
	JR NC,.L25
	CP '0'+0
	JP NC,.L24
.L25:
	scf  	;error was no digit
;3 	exit  	;leave procedure
	RET
;2 	endif
.L24:
;2 	while a in ['0'..'9']
.L26:
	CP '9'+1
	JR NC,.L29
	CP '0'+0
	JP NC,.L28
.L29:
	JP .L27
.L28:
	ld d,h
	ld e,l  	;multiply hl with 10
	add hl,hl
	add hl,hl
	add hl,de 	;*5
	add hl,hl 	;*10
	and 0fh 	;digit
	ld e,a
	ld d,0
	add hl,de 	;result value
	call ci
;2 	endwhile
	JP .L26
.L27:
;1 	endif
.L23:
	push af  	;save terminator
	ld a,(flag)
;1 	if a>0
	CP 0
	JP Z,.L30
	JP C,.L30
	ld de,0
	ex de,hl
	xor a
	sbc hl,de 	;complement
;1 	endif
.L30:
	pop af
	scf
	ccf  	;hl = value
	ret  	;no carry  akku=terminator


hexout:		;prints hl in hex
	ld a,h
	call nibble
	ld a,l
nibble:
	push af
	rrca
	rrca
	rrca
	rrca
	and 0fh
	call hexdigit
	pop af
	and 0fh
hexdigit:
;1 	if a in [10..15]
	CP 15+1
	JR NC,.L33
	CP 10+0
	JP NC,.L32
.L33:
	JP .L31
.L32:
	sub 10
	add a,'A'
;1 	else
	JP .L34
.L31:
	add a,'0'
;1 	endif
.L34:
	ld c,a
	call co
	ret
		;

		;
dezout:		;prints hl in dez
	ld c,0
	push bc  	;save flag on stack
	bit 7,h
;1 	if nz
	JP Z,.L35
	ld c,'-'
	call co
	ld de,0
	ex de,hl
	xor a
	sbc hl,de 	;complement if negative
;1 	endif
.L35:
		;
;1 	repeat
.L36:
		; hl := hl div 10
		;  a := hl mod 10
	ld a,0  	;overflow
;2 	do b,16 	;for each bit
	LD b,16 
.L37:
	sla l
	rl h
	rl a
	cp 10  	;div 10
;3 	if nc
	JP C,.L38
	sub 10
	set 0,l 
;3 	endif
.L38:
;2 	enddo
	DEC B
	JP NZ,.L37
	add a,'0'
	ld c,a
	push bc 	;save it
;1 	until h=0 and l=0
	LD A,h
	OR A
	JP NZ,.L36
	LD A,l
	OR A
	JP NZ,.L36
	pop bc
;1 	while c<>0
.L39:
	LD A,c
	OR A
	JP Z,.L40
	call co
	pop bc
;1 	endwhile
	JP .L39
.L40:
	ret


txt1:
	defm 'Pocket-Hex Calculator'
	defb 0dh,0ah
	defm 'Written in STRU by Rolf-D.Klein '
	defb 0dh,0ah,0

txt2:
	defb 0dh,0ah
	defm 'Enter Formula ->'
	defb 0


		; start
start:
	ld hl,txt1
	call print
;1 	loop
	PUSH HL
	LD HL,.L41
	EX (SP),HL
.L42:
	ld hl,txt2
	call print
	call getnum
;2 	exitif a = 3  	;CTRL-C stops
	CP  3  
	RET Z
;2 	while a in ['+','-']  
.L43:
	CP '+'
	JP Z,.L45
	CP '-'
	JP Z,.L45
	JP .L44
.L45:
;3 	if a = '+'
	CP  '+'
	JP NZ,.L46
	push hl
	call getnum
;4 	exitif a = 3
	CP  3
	RET Z
	pop de
	add hl,de
;3 	else
	JP .L47
.L46:
	push hl
	call getnum
;4 	exitif a = 3
	CP  3
	RET Z
	pop de
	push af
	xor a
	ex de,hl
	sbc hl,de
	pop af
;3 	endif
.L47:
;2 	endwhile
	JP .L43
.L44:
	ld c,' '
	call co
	call hexout
	ld c,' '
	call co
	call dezout
;1 	endloop
	JP .L42
.L41:
	call 0  	;warm boot
		;

flag:	defb 0 	;ram zell


	end start