option nolet  ! don't
!print "************************************************"
!print "* elek 1: interactive Ohms_Law 'version1'      *"
!print "* peter.vlasschaert@gmail.com ,15/05/2018      *"
!print "************************************************"
! filename :Ohmslawinteractiverversion1
do
call info
print
!****************************************************
! relation between 'current,voltage,resistance,power'
! power = P,current = I,voltage = V,resistance = R
! formula : def :'power'       P = V*I
!           def 'Ohms Law'     V = I*R
!****************************************************
call formula
! use function answer
declare function answer
print
print "**********"
print " input => "
print "**********"
print 
print "***********************************************************"
print "*'two values' from 'four values' ,values as input : result*"
print "***********************************************************"
print
call inp(V,I,R,P) 
print
! calculation of the unknowns
call cal(V,I,R,P)
! output result
print "***********"
print " result => "
print "***********"
print
call outp(V,I,R,P)
print
print "************************"
print " press any key:continue "
print " press enter  :end      "
print "************************"
print
pause 7
clear
loop until key input
end

SUB info
print "************************************************"
print "* elek 1: interactive Ohms_Law 'version1'      *"
print "* peter.vlasschaert@gmail.com ,15/05/2018      *"
print "************************************************"
END SUB

sub formula
print "**************************"
print "* FORMULA  =>            *"
print "**************************"
print
print "def :'power'       P = V*I = I^2*R"
print "def :'Ohms Law'    V = I*R        "
end sub

sub inp(V,I,R,P)
declare function answer
V = answer("Voltage    unit:(volts)")
I = answer("Current    unit:(amps) ")
R = answer("REsistance unit:(ohms) ")
P = answer("Power      unit:(watts)")
end sub

sub cal(V,I,R,P)
if v <> 0 and I<> 0 then
 R=V/I
 P= V*I
elseif V <>0 and R<>0 then
 I= V/R
 P= V^2/R
elseif V <> 0 and P<>0 then
  I=P/V
  R=V^2/P
elseif I <> 0 and R<>0 then
  V=I*R
  P=I^2*R
elseif I <> 0 and P <>0 then
  V=P/I
  R=P/I^2
elseif R<>0 and P<>0 then
  V=sqr(P*R)
  I=sqr(P/R)
else
  print " not enough information "
end if

end sub

sub outp(V,I,R,P)
print "Voltage    (V) = ";V
print "Current    (I) = ";I
print "Resistance (R) = ";R
print "Power      (P) = ";P
end sub

function answer(q$)
print q$;
line input x$
   when error in
        answer = val(x$)
   use
        answer = 0
   end when
end function