All hands must be assigned to an action

Our decision tree can only be computed if all hands in every player's range have been assigned to an action.

For example, let's see what happens if we delete the "Fold all hands" action from the decision point where small blind raises to 27. To do so, select the action by left-clicking it and press Del on your keyboard.

Now press F7 to compute the tree.
You'll get an error message from the software such as this one:

In this manner the software will tell you that after the point where BB raises to 9 it ran into a situation where a starting hand was not assigned to an action. The appropriate decision node has lighted up in red to make it more clear where exactly in the tree this happened. In this way you'll know you need to add an action or condition within this decision to deal with this starting hand.

An important exception

An important exception to this is the first decision a player makes preflop.
Namely, a player's initial range is decided in his first preflop decision.
This will be discussed in more detail on the next page.