Homework 1

CS 220

40 points, due Sept. 26, 1997

1. (10 pts.) Problem 2.11.

2. (30 pts.) Write a simple calculator program in SAL. Input to the program will be a single line of the form:

   x op y
   

   where x and y are non-negative integers and op is one of the four arithmetic operations. op is surrounded by a single space character on each side.

   Write a procedure to read a non-negative integer, character by character and use that procedure in your program. Here is the algorithm for reading a number, in case you've forgotten it:

   value = 0;
   c = getchar();
   while ('0' <= c && c <= '9')
   {
      value = 10 * value + c - '0';
      c = getchar();
   }
   

   Your program should validate its inputs before computing any results. Hand in a source SAL listing of your program and several sample runs (use script; see its man page).