Message Codes

Each message line in the Messages view contains a ‘P,’ ‘S,’ ‘s,’ or ‘R’ code. These codes have the following meanings:

Code	Meaning
P	The message was posted to the queue with the PostMessage function. No information is available concerning the ultimate disposition of the message.
S	The message was sent with the SendMessage function. This means that the sender doesn’t regain control until the receiver processes and returns the message. The receiver can, therefore, pass a return value back to the sender.
s	The message was sent, but security prevents access to the return value.
R	Each ‘S’ line has a corresponding ‘R’ (return) line that lists the message return value. Sometimes message calls are nested, which means that one message handler sends another message.