Each session configured by your emulator has both a long session name and a short session name.

The long session name can be up to eight characters long. The short session name is a single letter, such as "A" or "D". You specify a short session name when you are configuring your emulator, but usually the first session is called "A", the second session is "B", and so on. In some cases, if only a single session is available, the short session name may be "F". ECS subroutines use only short session names for denoting sessions.