BEGIN {
   myprompt = "(To Stop press CTRL+D) > "
   printf "Welcome to MyAddtion calculation awk program v0.1\n"
   printf "%s" ,myprompt
 }

{
   no1 = $1
   op  = $2
   no2 = $3
   ans = 0
   
   if ( op == "+" )
   {
      ans = $1 + $3
      printf "%d %c %d = %d\n" ,no1,op,no2,ans
      printf "%s" ,myprompt 
   }      
   else
   {
      printf "Opps!Error I only know how to add.\nSyntax: number1 +  number2\n"
      printf "%s" ,myprompt
   }      
}

END {
  printf "\nGoodbuy %s\n" , ENVIRON["USER"] 
}