# 1.61 while

    while <condition> [ loopname <loopname> ]
      <code>

The `while` command executes a block of commands repeatedly, checking the provided condition at the start of each iteration. If the condition is true, the loop executes again. This is similar to a `do` loop, except that the contents of a `while` loop may not be executed at all if the iteration criterion tests false upon the first iteration. For example, the following code prints out the low-valued Fibonacci numbers:

    i = 1
    j = 1
    while (j < 50)
     {
      print j
      i = i + j
      print i
      j = j + i
     }