Correct me if i'm wrong pls.....

[j_cart007]

here is my Caesar cipher code, can u pls have a look at it and correct me if i'm wrong.

AREA    text, CODE      

SWI_Exit	EQU	&11
SWI_WriteC	EQU	&0

                ENTRY                   

                ADR	r4, hello       
		ADR	r3, alpha
		ADR	r2, key
loop            
               
                LDRB    r0, [r4], #1    
		STRB	r0, [r4], #1
		CMP     r0, #0          
		BNE	check
		SWI_Exit 0x11
check           
		LDRB	r1, [r3], #1
		STRB	r1, [r3], #1
		CMP	r0, r1
		BNE	encrypt
       		B	loop         
encrypt
                LDRB	r5, [r2], #1
		STRB	r5,[r2], #1
		MOV	r0, r5
		STRB	r0,[r4], #1
		SWINE	SWI_WriteC		
		BEQ	endP
		B	loop	

hello	DCB     "THIS MESSEGE IS GOING TO BE ENCRYPTED ",0
alpha	DCB	"ABCDEFGHIJKLMNOPQRSTUVWXYZ",0
key	DCB	"XZYCJBTEKMGHONPEDCBAVWQLRU",0


endP

	MOV	pc, lr			; return
	END