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TITLE   H2D.ASM
;===== Konverterar ett inmatat HEX-tal till decimal form
;===== samt skriver ut det p† sk„rmen.
;========================================================================
        INCLUDE CONV.MAC
        INCLUDE SCREEN.MAC
        INCLUDE KEYB.MAC
;------------------------------------------------------------------------

CSEG    SEGMENT
        ASSUME CS:CSEG,DS:CSEG
        ORG 100h

start:  jmp begin

buffer db 7 dup (?)
par_flag db 0
;-----------------------------------------------------------------------

main    PROC NEAR
        
        call Param_Read
        jcxz get_going                    ;;CX <> 0 signalerar Error
        jmp Quit

Get_Going:
        cmp par_flag,1
        jz no_msg
        Print 'Converts Hexadecimal to Decimal, <Return> exits'
        cr_lf
no_msg:
        cr_lf
next_inp:
        cmp par_flag,1
        jz not_empty
        Print 'HEX value: '
        hex4_in                                 ;Get HEX input
        cmp bx,0000h
        jnz not_empty
        jmp Quit
not_empty:
        cmp par_flag,1
        jz no_tab
        tab 25
no_tab: Print 'Decimal value = '
        Hex2Dec buffer
        From_Buf Buffer
        cmp par_flag,1
        jz Quit
        cr_lf
        jmp next_inp
Quit:
        cr_lf
        ret

main    ENDP

;-------------------------------------------------------------------------

Param_Read PROC NEAR

        xor cx,cx                        ;;Nollst„ll error-flag

        cmp byte ptr ds:[80h],0
        jnz  par_exist
        jmp ready

par_exist:        
        mov par_flag,1

        mov di,081h
Skip_spaces:                            ;;Skippa inledande blanksteg
        Inc di
        cmp byte ptr[di],020h
        jz Skip_Spaces

        xor bx,bx                       ;;Nollst„ll tecken_r„knare
        xor dx,dx                       ;;Nollst„ll DX-register

Next_Char:
        mov al,[di]
        cmp al,0dh                      ;; <RET> avslutar inmatning
        jz Ready

        cmp al,020h                     ;;Till†t space i slutet av str„ngen
        jnz no_spc
        jmp chk_end

no_spc: cmp al,'0'                      ;;Error if lower than '0'
        jl  Error
        cmp al,'9'
        jle Save                        ;;Save if Lower or Equal '9'
        and al,0dfh                     ;;gemener -> VERSALER
        cmp al,'A'                      ;;Error if lower than 'A'
        jl Error
        cmp al,'F'                      
        jle Save                        ;;Save if lower or equal 'F'

Error:
        Print 'Wrong input format, Aborted'
        mov cx,0ffffh
        jmp Ready

Save:
        inc bx
        cmp bx,05h
        jz  Ready

        sub al,30h                      ;;ASCII -> HEX
        cmp al,0ah                      ;;V„rdet j„mf med 10 dec
        jc  Siffra                      ;; Hopp om 0-9
        sub al,07h                      ;;eljest minska med 7

Siffra:
        cbw                             ;;Byte -> Word
        push cx                         ;;Spara error-flagga
        mov cl,04h                      ;;F”rbered shift 4 ggr
        sal dx,cl                       ;;Skifta 4 ggr
        pop cx
        add dx,ax                       ;;Spara i DX

        inc di
        jmp Next_Char                   

ready:
        ret

chk_end:
more_spc:
        inc di
        cmp byte ptr[di],020h                
        jz more_spc
        cmp byte ptr[di],0dh
        jnz Error
        jmp ready

Param_Read ENDP

;-------------------------------------------------------------------------

begin:
        call main
        ret
 
CSEG    ENDS
END     start
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