random

; x[i + 1] = (A * x[i] + B) mod N - pseudo-random numbers formula
; N depends on platform (for example, 32-bit -> 2^32)

        org 100h

EntryPoint:
        call    Random.Initialize
.GenerateLoop:
        call    Random.Get

        push    ax
        call    PrintHex

        mov     ax, $0C08
        int     21h
        test    al, al
        jnz     @F
        mov     ah, $08
        int     21h
@@:
        jmp     .GenerateLoop
        ret

; Registers:
;   Overwrites AX, CX, DX.
;
PrintHex:
        push    bp
        mov     bp, sp
        push    bx

        mov     bx, [bp + 4]
        mov     cx, 4
.PrintLoop:
        rol     bx, 4
        mov     ax, bx
        and     ax, 0000'0000_0000'1111b

        cmp     al, $0A
        sbb     al, $69
        das

        mov     dl, al
        mov     ah, $02
        int     21h
        loop    .PrintLoop

        pop     bx
        pop     bp
        ret     2

Random.Initialize:
        mov     ah, 02Ch
        int     21h
        mov     [Random.wPrev], dx
        ret

Random.Get:
        mov     ax, [Random.wPrev]
        rol     ax, 7
        adc     ax, 23
        mov     [Random.wPrev], ax
        ret

Random.wPrev    dw      ?