Boolean

A boolean value is a toggle used in programming that is inherently exclusively either "on" or "off". When enabled it is denoted with true or 1, and with false or 0 when disabled, depending on the syntax of the language being used.

Its use varies in different areas of the engine:

• C++ code generally uses true / false, which occupies 1 byte.
• The unmodified Half-Life SDK uses BOOL to represent boolean values, it is a typedef for int; therefore it uses 4 bytes instead of 1.
• Materials use 1 / 0
• Weapon Scripts use 1 / 0
• .VMF files use 1 / 0
• .DMX files
  Todo: Verify how, and which form
• .VCD files use 1 / 0

Certain file types used in Source also do not typically use booleans:

• .QC files
• .SMD files