DisplayResult.s

	AREA	DisplayResult, CODE, READONLY
	IMPORT	main
	IMPORT	getkey
	IMPORT	sendchar
	EXPORT	start
	PRESERVE8
	;This code belongs to Hannah Keating, JF TCD student
start
	MOV R4, #0			;	result = 0 
	MOV R5, #0			; 	finalAns = 0 
	MOV R6,#10			;	
	MOV R10, #0			;	addFirstNum = 0 	
	MOV R11, #0			; 	subFirstNum = 0 
	MOV R12, #0			; 	mulFirstNum = 0 
	MOV R7, #0			;   powerFirstNum =0
	
read					;	start of while loop 	
	
	BL	getkey			; 	read key from console
	CMP R0,#0x30		;	if ( key >= '0') 
	BLO notNum			; 	{ 
	CMP R0,#0x39		;	if (key <= '9') 
	BHI notNum 			;	{ 	
	
	BL	sendchar		;   echo key back to console
	
	MUL R4,R6,R4 		;	result = result *10; 
	SUB R0,R0,#0x30 	; 	convert Ascii to number 
	ADD R4, R0, R4		; 	Result = result + value 

 B read					; 	}
 
notNum
 	CMP	R0, #0x0D  		; 	if (key == ENTER)
	BEQ	endRead			; 	{
	
	CMP R0, #0x08		; 	else if( key == BACKSPACE) 
	BEQ backspace		; 	{
	
	CMP R0, #0x2B		; 	else if( key == '+') 
	BEQ addchar			; 	{
	
	CMP R0, #0x2D		; 	else if( key == '-') 
	BEQ subchar			; 	{
		
	CMP R0, #0x2A		; 	else if( key == '*') 
	BEQ mulchar			; 	{
	
	CMP R0, #0x5e		; 	else if( key == '^') 
	BEQ powerchar		; 	{
	B read				; 	}

	;This code belongs to Hannah Keating, JF TCD student
backspace 				; 	undo inputed value  
	BL	sendchar		; 	echo key back to console
	
	SUB R0,R0,#0x30 	; 	convert Ascii to number 
	SUB R4, R4, R0 		; 	Result = result - value 
 B  devideby10			; 	Result = Result / 10; 	
	
devideby10				; 
	LDR R9, = 0			; 	Quotient = 0 
	MOV R8, R4			; 	remainder = a 
while	
	CMP R8, R6			; 	while( remainder >= 10) 
	BLO	endwh			; 	{ 
	ADD R9,R9,#1		; 	Quotient = Quotient + 1 
	SUB R8, R8, R6 		; 	Remainder = remainder - 10 
	B while				;	}
endwh	
	SUB R9,R9,#4 		; 	To prevent a error with Quotient 
	MOV R4, R9			; 	sets result = Quotient
	
	 B	read			; 	}	
	 
addchar
	MOV R10, R4			;	addFirstNum = result  
	MOV R4, #0			; 	reset input
	BL	sendchar		;   echo key back to console
	B	read			;	}	
	 
subchar
	MOV R11, R4			; 	SubFirstNum = result 
	MOV R4, #0			; 	reset input
	BL	sendchar		;   echo key back to console
	B	read			; 	}	
	
mulchar
	MOV R12, R4			;	mulFirstNum = result 
	MOV R4, #0			; 	reset input
	BL	sendchar		;   echo key back to console
	B	read			; 	}	

powerchar
	MOV R7, R4			;	powerFirstNum = result 
	MOV R4, #0			; 	reset input
	BL	sendchar		;   echo key back to console
	B	read			;	 }	
	
	
endRead					; 
	CMP R10, #0			; 	if ( addFirstNum != 0)
	BEQ notadd			; 	{ 	
	ADD R5,R10, R4		; 	finalAns = addFirstNum + result

notadd

	CMP R11, #0			; 	if ( subFirstNum != 0)
	BEQ notsub			; 	{ 	
	SUB R5,R11,R4		;	finalAns = subFirstNum - result

notsub

	CMP R12, #0			; 	if ( mulFirstNum != 0)
	BEQ notmul			; 	{ 	
	MUL R5,R12,R4		; 	finalAns = mulFirstNum * result

notmul
	;This code belongs to Hannah Keating, JF TCD student
	CMP R7, #0			; 	if ( powerFirstNum != 0)
	BEQ notpower		; 	{ 
	MOV R6, #1			; 	powerStore =1	
powerwhile 				; 
	CMP R4, #0			; 	while( result !=0 ) 
	BEQ endpowerwh		; 	{ 
	MUL R6,R7,R6		; 	powerStore = powerFirstNum * powerStore
	SUB R4, R4, #1		; 	result = result -1 
	b 	powerwhile 		; 	} 
endpowerwh
	MOV R5, R6			; 	finalAns = powerStore
notpower

	MOV R4, #0			; preventLeadZero = 0 
	MOV R6, #10			; base = 10 
	MOV R7, # 15 		; power = 15
	LDR R0, = 0x3D		; sets display to '=' 
	BL	sendchar		; Send = to console 
	
	CMP R5,R6			; if( finalAns >= base)
	BLO firstDigit		; 
	;This code belongs to Hannah Keating, JF TCD student
displayResult 
	CMP R5, #0			; while( finalAns >0) 
	BLO	firstDigit		; { 
	B 	computeTenPower	; find relatvant power of ten 	
	
computeTenPower
	MOV R8, R7			;  	computePower= power
	MOV R9, #1			; 	powerStore =1	
	
computewhile 			; 
	CMP R8, #0			; 	while( computePower !=0 ) 
	BEQ endcomputwh		; 	{ 
	MUL R9,R6,R9		; 	powerStore = base * powerStore
	SUB R8, R8, #1		; 	computePower = computePower -1 
	b 	computewhile 	; 	}
	
	;This code belongs to Hannah Keating, JF TCD student
endcomputwh	
	SUB R7, R7, #1		;  power = power -1
	CMP R5, R9			;  if( finalAws < powerStore)
	BHS displayDevide	;  AND
	CMP R4, #0			; if (preventLeadZero !=0) 
	BEQ displayResult	; {

	
displayDevide			;
	ADD R4, R4, #1		; preventLeadZero = preventLeadZero + 1
	LDR R10, =0			; Quotient = 0 
	MOV R11, R5			; remainder = finalAns
	
whileresult 	
	CMP R11, R9			; while( remainder >= powerStore)  
	BLO	endwhresult		; { 
	ADD R10,R10,#1		; Quotient = Quotient + 1 
	SUB R11, R11, R9 	; Remainder = remainder - powerStore 
	B whileresult		;}
endwhresult	
	MOV R0, R10			; display = Quotient
	MOV R5, R11			; finalAws = remainder  
	ADD R0, R0,#0x30	; Convert to Ascii 
	BL	sendchar		; echo display back to console
	B	displayResult	; }	
	
firstDigit				; 
	MOV R0, R5			; display = finalAws
	ADD R0, R0,#0x30	; Convert to Ascii 
	BL	sendchar		; echo display back to console
	
stop	B	stop
	;This code belongs to Hannah Keating, JF TCD student
	END