This demonstrates normal division (which produces rational numbers when possible), <CODE>div</CODE>, and <CODE>mod</CODE>.  <CODE>div</CODE> rounds toward negative infinity (defined as <CODE>floor[x/y]</CODE>).  <CODE>mod</CODE> uses the sign of the second number (defined as <CODE>x - y * floor[x/y]</CODE>).  All operators automatically produce big integers or exact rational numbers when necessary.

[a,b] = input["Enter numbers",["a","b"]]
ops=["+", "-", "*", "/", "div" ,"mod" ,"^"]
for op = ops
{
   str = "$a $op $b"
   println["$str = " + eval[str]]
}