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Source code

;bits 16.  IDK how to get Godbolt to show 16-bit disassembly

mov si, table
    ; di -> start      ; DI could be used instead of BX earlier
                       ; so we can clobber BX for BIOS calls
loop_table:
        mov al, ' '
        call disp_al
        lodsb
        call disp_al
        lodsb
        call disp_al
        cmp al, ' '
        jbe .next
        mov al, '='
        call disp_al

mov ax, [di]
        inc di
        inc di           ; scasw would increment DI by 2, but be slower and need ES set sanely to not read an MMIO port or something
        call disp_ax_hex
.next:
        cmp si, table.end
        jb loop_table

exit:
        xor ax, ax
        int 16h
        int 19h

disp_al:                        ; clobbers AH, BX and maybe BP
                                ; AL is preserved
        mov ah, 0Eh
        mov bx, 7
        int 10h
        retn

disp_ax_hex:          ; clobbers CX, DX, BX and BP
                      ; AX rotates back to is original value
;    push  cx
;    push  dx
    mov   dx, 4
    mov   cl, 4       ; rotate count
.digit_loop:
        rol   ax, cl
        push  ax
        and   al, 0xf
        add   al,'0'                      ; if number is 0-9, now it's the correct character
        cmp   al,'9'
        jna   .decimalnum          ; if we get decimal number with this, ok -->
        add   al,7                        ;  otherwise, add 7 and we are inside our alphabet
.decimalnum:
        call  disp_al
        pop   ax
        dec   dx
        jnz  .digit_loop
;    pop   dx
;    pop   cx
    ret

align 2
table:
        dw "SS"
        dw "BP"
        dw "SP"
        dw "CS"
        dw "IP"
        dw "FL"
        db 13,10
        dw "DS"
        dw "SI"
        dw "ES"
        dw "DI"
        db 13,10
        dw "AX"
        dw "BX"
        dw "CX"
        dw "DX"
        db 13,10
.end: