I am trying to write a simple program to manipulate some values and display them at certain "checkpoints." I have the first checkpoint, checkpoint A, at the beginning of the program before anything has been moved, but I still am getting unexpected values in the output. Can someone please tell me where my mistake lies?


;================================================= ==
DOSSEG
.MODEL SMALL,BASIC
;================================================= ========

EXTRN PUTHEX:FAR
EXTRN PUTSTRNG:FAR ;DISPLAY CHARACTER STRING
EXTRN NEWLINE:FAR ;DISPLAY NEWLINE CHARACTER

;
; S T A C K S E G M E N T D E F I N I T I O N
;
.STACK 256
;================================================= ========
;
; D A T A S E G M E N T D E F I N I T I O N
;
.DATA
ALPHA DB 250
BETA DW 01ABH
GAMMA DW 45EFH
LAMDA DB CONSTANT
OMEGA DW 67CDH
CONSTANT EQU 10001001B
;
;================================================= ========
;
; C O D E S E G M E N T D E F I N I T I O N
;
.CODE
ASSUME DS:NOTHING,ES:DGROUP
PR_2_2:
MOV AX,DGROUP ;SET ES-REGISTER TO POINT TO
MOV ES,AX ;CONSTANT DATA SEGMENT
;*** CHECKPOINT A ***
MOV BL,0 ;CODE FOR 8 BIT
XCHG AL,ALPHA ;SWAP WITH AL
CALL PUTHEX ;DISPLAY AL IN HEX
XCHG AL,ALPHA ;RESTORE AL AND ALPHA TO PREVIOUS VALUES
CALL NEWLINE

MOV BL,1
XCHG AX,BETA
CALL PUTHEX
XCHG AX,BETA
CALL NEWLINE

MOV BL,1
XCHG AX,GAMMA
CALL PUTHEX
XCHG AX,GAMMA
CALL NEWLINE

MOV BL,0
XCHG AL,LAMDA
CALL PUTHEX
XCHG AL,LAMDA
CALL NEWLINE

MOV BL,1
XCHG AX,OMEGA
CALL PUTHEX
XCHG AX,OMEGA
CALL NEWLINE

MOV AH,CONSTANT
MOV AL,ALPHA
MOV BX,GAMMA
XCHG AH,BH
XCHG AX,BETA
MOV ALPHA,AH
MOV LAMDA,AL
;*** CHECKPOINT B ***
MOV BL,0 ;CODE FOR 8 BIT
XCHG AL,ALPHA ;SWAP WITH AL
CALL PUTHEX ;DISPLAY AL IN HEX
XCHG AL,ALPHA ;RESTORE AL AND ALPHA TO PREVIOUS VALUES
CALL NEWLINE

MOV BL,1
XCHG AX,BETA
CALL PUTHEX
XCHG AX,BETA
CALL NEWLINE

MOV BL,1
XCHG AX,GAMMA
CALL PUTHEX
XCHG AX,GAMMA
CALL NEWLINE

MOV BL,0
XCHG AL,LAMDA
CALL PUTHEX
XCHG AL,LAMDA
CALL NEWLINE

MOV BL,1
XCHG AX,OMEGA
CALL PUTHEX
XCHG AX,OMEGA
CALL NEWLINE


MOV CX,OMEGA
XCHG BL,CH
MOV GAMMA,BX
MOV OMEGA,CX
;*** CHECKPOINT C ***
MOV BL,0 ;CODE FOR 8 BIT
XCHG AL,ALPHA ;SWAP WITH AL
CALL PUTHEX ;DISPLAY AL IN HEX
XCHG AL,ALPHA ;RESTORE AL AND ALPHA TO PREVIOUS VALUES
CALL NEWLINE

MOV BL,1
XCHG AX,BETA
CALL PUTHEX
XCHG AX,BETA
CALL NEWLINE

MOV BL,1
XCHG AX,GAMMA
CALL PUTHEX
XCHG AX,GAMMA
CALL NEWLINE

MOV BL,0
XCHG AL,LAMDA
CALL PUTHEX
XCHG AL,LAMDA
CALL NEWLINE

MOV BL,1
XCHG AX,OMEGA
CALL PUTHEX
XCHG AX,OMEGA
CALL NEWLINE
.EXIT ;RETURN TO DOS

END PR_2_2