c exempel av 1-dimensionell vaermeledning
c 
       dimension x(10),told(10),t(10),ae(10),aw(10),b(10)
c 
       data x/0.,1.,3.,4.,4.5,5*0.0/ 
c 
c randvaerden 
       t(1)=1. 
       t(6)=10. 
c 
c antal noder ni 
       ni=6 
c 
c goer max. 100 iterationer 
       do n=1,100 
c goer en loop oever alla noder (utom randnoderna) 
         do i=2,ni-1 
c ber. dx_w 
            if (i.eq.2) then 
               dx_w=0.5*(x(2)-x(1)) 
            else 
               dx_w=0.5*(x(i)-x(i-2)) 
            end if 
c ber. dx_e 
            if (i.eq.ni-1) then 
               dx_e=0.5*(x(ni-1)-x(ni-2)) 
            else 
               dx_e=0.5*(x(i+1)-x(i-1)) 
            end if 
c ber. deltax 
            deltax=x(i)-x(i-1) 
  
c ***ber. ae,aw,b (konduktivitetskoeff. k=konst=1) 
            ae(i)=1./dx_e 
            aw(i)=1./dx_w 
            b(i)=2.*deltax 
c ber. ap 
            ap=ae(i)+aw(i) 
c spara gamla 't' i 'told' 
            told(i)=t(i) 
            t(i)=(ae(i)*t(i+1)+aw(i)*t(i-1)+b(i))/ap 
         end do 
c beraekna felet 
         fel=0. 
         do i=2,ni-1 
            fel=fel+abs(t(i)-told(i)) 
         end do 
         write(6,*)'n,fel',n,fel 
c om felet < 0.001, avbryt beraekningarna 
         if (fel.lt.0.001) goto 100 
       end do 
100    continue 
c 
c skriv ut svaret paa filen 'resultat.txt' 
       open(unit=10,file='resultat.txt',status='unknown') 
       write(10,201) 
       do i=1,ni 
          write(10,203)i,t(i) 
       end do 
 201   format(1x,t5,'nodnummer',t20,'temperatur') 
 203   format(1x,t7,i3,t20,1pe10.3) 
       close(10) 
c 
       stop 
       end