Fahrenheit Temperature                                       Centrigade Temperature
-----------------------                                       ---------------------
1                                                                      -17
----------------------                                         --------------------
3                                                                      -13
----------------------                                        ---------------------
89                                                                      31
----------------------                                       -----------------------
etc.

#!/bin/sh
print_dash_line()
{
#sub function to print dashes
echo "_ _ _ _ _ _ _ _ _ _ _ _        _ _ _ _ _ _ _ _ _ _ _ _ "
}
#***** Start of Main Program *****
#***** Assign Variables
input_file=data.file
output_file=ans.file
# formula ft=(9/5)*ct+32
# formula ct=(5/9)*(ft-32)
echo "1. Convert Centigrade temperature into Fahrenheit"
echo "2. Convert Fahrenheit temperature into Centigrade"
echo -n "Select your choice (1-2) : "
read choice
if [ $choice -eq 1 ]
then
   echo -n "Enter Centigrade Temperature : "
   set `cat $input_file`
   echo $1 $2 $3 $4
   read ct
   ft=$(echo "scale=2;((9/5) * $ct) + 32" |bc)
   echo " Centigrade Temperature        Fahrenheit Temperature " > $output_file
   print_dash_line  >> $output_file
   echo >> $output_file
   echo "          $ct                           $ft " >> $output_file
   print_dash_line >> $output_file
elif [ $choice -eq 2 ]
then
   echo -n "Enter Fahrenheit Temperature : "
   set `cat $input_file`
   echo $1 $2 $3 $4
   read ft
   ct=$(echo "scale=2; (5/9)*($ft-32)" |bc)
   echo " Fahrenheit Temperature        Centigrade Temperature " > $output_file
   print_dash_line  >> $output_file
   echo >> $output_file
   echo "          $ft                          $ct " >> $output_file
   print_dash_line >> $output_file
else
    echo "Please select 1 or 2"
    exit l
fi