Lab Test question 1

; calculation of a+b-c

.MODEL SMALL   ; IN THIS COURSE ALL MODEL ARE SMALL
.STACK 100H    ; WE ALWAYS USE STACK 100H


.DATA     ; DATA SEGMENT

    SN_N1 DB "Enter first number: $"             ; we store the string here
    SN_N2 DB 0DH,0AH,"Enter second number: $"    ; we store the string here
    SN_N3 DB 0DH,0AH,"Enter third number: $"    ; we store the string here

    SN_STR1 DB 0AH,0DH,'CALCULATION OF '     ; PRINT A NEW LINE AFTER TAKING INPUT SO WE USE 0AH,0DH
    SN_FIRSTNUM DB ?                      ; TAKE A VARIABLE WHERE WE TAKE FIRST NUMBER
    SN_STR DB ","                          ; GIVE A COMMA (,) HERE
    SN_SECONDNUM DB ?                     ; TAKE A VARIABLE WHERE WE TAKE SECOND NUMBER
    SN_STR2 DB ' AND '                   ; ASSIGN A STRING IN STR 2
    SN_THIRDNUM DB ?                    ; TAKING THIRD NUMBER
    SN_STR3 DB ' IS '                    ; ASSIGN ANOTHER STRING IN STR3
    SN_ANS DB ?                          ; TAKE A VARIABLE WHERE WE WILL PUT OUT SUMMATION, AND DO NOT END THE STRING BY $ SIGN
    SN_STR4 DB ' $'                      ; ASSIGN $ HERE SO ALL AVOBE STRING ARE PRINT TOGETHER



.CODE

MAIN PROC       ; MAIN CODE START HERE

    ;PROGRAMME SEGMENT PREFIX
    MOV AX,@DATA
    MOV DS,AX    ; INITILATION OF DS

    MOV AH,9        ; TO PRINT STRING WE USE IT
    LEA DX,SN_N1     ; LOADED THE STRING          LEA = LOAD EFFICTIVE ADDRESS
    INT 21H         ; THIS WILL PRINT THE LINE
    MOV AH,1            ; TAKING SOME INPUT
    INT 21H             ; INTRUPT THE WORK
    MOV BL,AL           ; IF WE TAKE INPUT GENERALY GOES TO AL SO WE MOVE THE INPUT VALUE INTO BL
    MOV SN_FIRSTNUM,AL  ; MOVE TO FIRSTNUMBER


    MOV AH,9        ; TO PRINT STRING WE USE IT
    LEA DX,SN_N2     ; LOADED THE STRING
    INT 21H         ; THIS WILL PRINT THE LINE
    MOV AH,1            ; TAKING SOME INPUT
    INT 21H             ; INTRUPT THE WORK
    MOV CL,AL           ; IF WE TAKE INPUT GENERALY GOES TO AL SO WE MOVE THE INPUT VALUE INTO BL
    MOV SN_SECONDNUM,AL    ; MOVE TO SECOND NUMBER

    MOV AH,9        ; TO PRINT STRING WE USE IT
    LEA DX,SN_N2     ; LOADED THE STRING
    INT 21H         ; THIS WILL PRINT THE LINE
    MOV AH,1             ; TO TAKE INPUT
    INT 21H              ; TAKE THIRD NUMBER HERE
    MOV SN_THIRDNUM,AL   ; MOVE THIRD NUMBER TO THIRDNUM VARIABLE


    ADD BL,CL            ; ADD FIRST TWO NUMBER HERE
    SUB BL,30H           ; CONVERT IT FROM ASCII TO INTEGER

    SUB BL,AL      ; HERE WE SUBTRACT BL AND AL
    ADD BL,30H     ; TO COVERT ASCII TO DECIMAL WE ADDED 30 FROM SUBTRACT VALUE     BL + 30 = BL ,   NOW IT IS DECIMAL.. CHECK ASCII TO  UNDERSTAND BETTER
    MOV SN_ANS,BL     ; NOW MOVE THE VALUE INTO ANSWER

    MOV AH,9      ; PRINT STRING
    LEA DX,SN_STR1   ; VARIABLE PRINTING FIRST TO LAST  BECAUSE WE USE $ AT LAST. SO IT PRINT FIRST TO LAST
    INT 21H       ; INTRUPT THE WORK



    MOV AX,4CH ; TERMINATED THE CODE AND EXIT
    INT 21H
    MAIN ENDP
END MAIN