I don't know the meanings of the directional signs.

Directional signs in Microsoft technologies usually refer to attributes or values that indicate where data is coming from and where it is going.

In Remote Procedure Call (RPC) and MIDL (Microsoft Interface Definition Language), directional attributes are applied to parameters of a function to describe the data flow:

• in
  • Meaning: The parameter value is passed from the caller to the function.
  • Use: The function receives data but is not required to modify or return it.
• out
  • Meaning: The parameter value is passed from the function back to the caller.
  • Use: The function writes data into this parameter to return results.
• in, out together
  • Meaning: The parameter is both supplied by the caller and modified/returned by the function.
  • Note: Using both increases call overhead, so it is used only when necessary.

These directional attributes are attached to parameters in IDL/MIDL definitions to control marshaling and data transfer behavior between client and server.

Separately, some APIs define direction enumerations to represent spatial directions. For example, in the Minecraft Bedrock Script API, the Direction enumeration uses named constants:

• Up – above (y + 1)
• Down – below (y - 1)
• North – along +z
• South – along -z
• East – along +x
• West – along -x

These values are used to specify relative directions in a 3D coordinate system.

References:

• Directional Attributes
• Combining Pointer and Directional Attributes
• Direction Enumeration