FTOA and ATOF procedure assembly for 80387

exp6.asm

.model SMALL
.386
.STACK 100H

.DATA
TEMP DW ?
NUMB REAL4 ?
STRING DB 1024 DUP(0)
WHOLE DD ?
FRACT DD ?
TEN REAL4 10.0

MINUS DB 0
POINT DB 0
DIGIT DW 0

.CODE
.STARTUP

; fill in your code

.EXIT

ATOF PROC NEAR USES EAX EBX ECX ESI
	; from Introduction to 80x86 Assembly Language and Computer Architecture
	; store from STRING to NUMB
	MOV MINUS, 0
	MOV POINT, 0
	FINIT
	FLD1  ; push 1
	FLDZ  ; push 0
	
	XOR ECX, ECX
	CMP STRING[ECX], '-'
	JNE CHECKPNT
	MOV MINUS, 1
	INC ECX
	CHECKPNT:
		MOV AL, STRING[ECX]
		CMP AL, '.'
		JNE ENDPOINT
		MOV POINT, 1
		JMP NEXTCHAR
	ENDPOINT:
		CMP AL, '0'
		JL NOTDIGIT
		CMP AL, '9'
		JG NOTDIGIT
		AND AX, 0FH
		MOV DIGIT, AX
		FMUL TEN
		FIADD DIGIT
		CMP POINT, 1
		JNE NEXTCHAR
		FXCH
		FMUL TEN
		FXCH
	NEXTCHAR:
		INC ECX
		JMP CHECKPNT
	NOTDIGIT:
		FDIVR
		CMP MINUS, 1
		JNE ATOF_RET
		FCHS
	ATOF_RET:
		FST NUMB
		RET

ATOF ENDP
	
FTOA PROC NEAR USES EBX ECX EDX
	; from The Intel Microprocessors (8th Edition)
	; it may not work in corner cases
	FINIT
	MOV ECX, 0
	FSTCW TEMP
	MOV AX, TEMP
	PUSH AX
	OR AX, 0C00H
	MOV TEMP, AX
	FLDCW TEMP
	FLD NUMB
	FTST
	FSTSW AX
	AND AX, 4500H
	.IF AX == 100H
		MOV STRING[ECX], '-'
		INC ECX
		FABS
	.ENDIF
	FRNDINT
	FIST WHOLE
	FLD NUMB
	FABS
	FSUBR
	FSTP FRACT
	MOV EAX, WHOLE
	MOV EBX, 10
	PUSH EBX
	.REPEAT
		MOV EDX, 0
		DIV EBX
		ADD DL, 30H
		PUSH EDX
	.UNTIL EAX == 0
	POP EDX
	.WHILE EDX != 10
		POP EBX
		MOV STRING[ECX], DL
		INC ECX
		MOV EDX, EBX
	.ENDW
	MOV STRING[ECX], '.'
	INC ECX
	POP TEMP
	FLDCW TEMP
	FLD FRACT
	.REPEAT
		; INC EDX
		FMUL TEN
		FIST TEMP
		MOV AX, TEMP
		ADD AL, 30H
		CALL ISDIGIT
		CMP BL, 1
		JNE FTOA_RET
		MOV STRING[ECX], AL
		INC ECX
		FISUB TEMP
		FXAM
		FSTSW AX
		SAHF
	.UNTIL ZERO?
	FTOA_RET:
		MOV STRING[ECX], '$'
		RET
	
FTOA ENDP

END