Smallest Program Witha Bug

In JavaLanguage:

  public class Buggy
  {
    public static voi main( String [] args )
    {
         System.out.println( 0.1 );
    }
  }

There's a 'd' missing from 'void'. So how many bugs are in this Java code??

In GNU SmallTalk:

 0.1 print

In SmallTalk 80:

 0.1
 (printIt)

In PythonLanguage:

 print repr(0.1)

or better yet

 b

ExBase:

 ? 1/0    (Similar to "print(1.0 / 0.0);" in C-like langs)

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Is the referred-to "bug" the fact that 0.1 is not exactly representable in IEEE 754 floating point? One could argue that the program is behaving correctly...

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There's an old programming proverb to the effect that "all programs have at least one bug and at least one redundant instruction". Iteratively, then, all programs can be reduced to a single instruction that doesn't work.

abort() ???

A friend has a story that illustrates the truth of this. Somewhere in an IBM mainframe OS (I don't know which one), there was a module that contained but a single instruction (it was a privilege-switching module). It was like that for several years. Eventually, a circumstance was discovered when it didn't work, and a bug report was raised. So the one instruction program did indeed have a bug. Apparently it's 13 instructions now.

From the context, there's every reason to think that this was a hardware bug, and that the extra dozen instructions were a work-around, not a fix for a software bug.

---

There's another IBM mainframe story, to the effect that someone wanted to write a program that did nothing, so they wrote one that said

     BR    15 

Then someone pointed out that it should really say

     BR    14

(because programs are usually called using a BALR 14,15). Then someone else pointed out that the return code (in register 15) was unpredictable, so it would be better to write

     SR    15,15
     BR    14

2 statements - 2 bugs!