More Information About Atoms

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows versions 3.0 and 3.1

SUMMARY

The following are questions on Atoms that expand on the description of Atoms:

1. Q. Is it reasonable to use Atoms to store strings of data?

   A. Yes, you can store constant strings of data using Atoms.

2. Q. Why is there no Atom for a null string?

   A. There is no Atom for a null string because none is defined.

3. Q. How are Atoms stored?

   A. Atoms are hashed with bucket chaining used to resolve
      collisions. The memory for the Atoms is allocated out of the
      caller's DS. The overhead per Atom is 9 bytes (4 for the memory
      arena, 5 for the Atom structure).

4. Q. What is the penalty for declaring many Atoms and then only using
      a few?

   A. The only consequences of declaring many Atoms and then only
      using a few are the consumption of memory and the increased
      chain of collisions.

5. Q. Are there reasonable limits to the number of strings that can be
      stored as Atoms?

   A. The absolute limit to the number of strings that can be stored
      as Atoms is the size of the caller's data segment.

6. Q. Is there any way to share Atoms between two instances of a
      program?

   A. To share Atoms between two instances of a program, have a shared
      library .EXE file with a single data segment that holds the
      Atoms to be shared. The Windows user interface code is an
      example of this.

7. Q. Is there a limit to the number of characters in a string that is
      being stored as an Atom?

   A. The limit to the number of characters in a string being stored
      as an Atom currently is 255.

8. Q. Are Atoms movable?

   A. Atoms are constants, and therefore are not movable.

9. Q. Do Atoms get swapped?

   A. Atoms do not get swapped.