.model small
          .code
          org    100h

kronos:   jmp    body
jumpfar   db     0eah
oldint    dw     0,0
oldtime   db     "PETER2000",3 dup(0)
message   db     "Tempo trascorso: ",0,0,3ah,0,0,3ah,0,0,0dh,0ah,24h

body      proc   near
          mov    ax,3550h
          int    21h
          mov    di,bx
          add    di,5
          lea    si,oldtime
          cld
          mov    cx,9
repe      cmpsb    
          jne    install
          mov    ah,2ch
          int    21h
          sub    dh,byte ptr es:[bx+14]
          sbb    cl,byte ptr es:[bx+15]
          sbb    ch,byte ptr es:[bx+16]
          cmp    dh,0
          jge    minutes
          add    dh,3ch
minutes:  cmp    cl,0
          jge    hours
          add    cl,3ch
hours:    cmp    ch,0
          jge    store
          add    ch,18h
store:    lea    di,message+11h
          push   es
          push   es
          push   cs
          pop    es
          mov    al,ch
          call   decim
          mov    al,cl
          call   decim
          mov    al,dh
          call   decim
          lea    dx,message
          mov    ah,9
          int    21h
disinst:  lea    dx,oldint
          mov    ax,2550h
          int    21h
          pop    es
          mov    es,es:[2ch]
          mov    ah,49h
          int    21h
          pop    es
          mov    ah,49h
          int    21h
          int    20h
install:  mov    cs:[oldint],bx
          mov    bx,es
          mov    cs:[oldint+2],bx
          push   cs
          pop    ds
          lea    dx,jumpfar
          mov    ax,2550h
          int    21h
          mov    ah,2ch
          int    21h
          mov    byte ptr cs:[oldtime+9],dh
          mov    byte ptr cs:[oldtime+10],cl
          mov    byte ptr cs:[oldtime+11],ch
          lea    dx,message
          int    27h
body      endp

decim     proc   near
          aam
          xchg   ah,al
          add    ax,3030h
          stosw
          inc    di
          retn
decim     endp

          end    kronos