'Freebasic .9
'Custom rounding
#define round(x,N) Rtrim(Rtrim(Left(Str((x)+(.5*Sgn((x)))/(10^(N))),Instr(Str((x)+(.5*Sgn((x)))/(10^(N))),".")+(N)),"0"),".")

#macro Euler(fn,_y,min,max,h,printoption)
Print "Step ";#h;":":Print
Print "time","Euler"," Analytic"
If printoption<>"print" Then Print "Data omitted ..."
Scope
    Dim As Double temp=(min),y=(_y)
    Do
        If printoption="print" Then Print temp,round(y,3),20+80*Exp(-0.07*temp)
        y=y+(h)*(fn)
        temp=temp+(h)
    Loop Until temp>(max)
    Print"________________"
    Print
End Scope
#endmacro

Euler(-.07*(y-20),100,0,100,2,"don't print")
Euler(-.07*(y-20),100,0,100,5,"print")
Euler(-.07*(y-20),100,0,100,10,"print")
Sleep