while repetition statement (p. 114) allows you to specify that a program should repeat an action while some condition remains true.
• The UML’s merge (p. 114) symbol joins two flows of activity into one.
• The decision and merge symbols can be distinguished by the number of incoming and outgoing transition arrows. A decision symbol has one transition arrow pointing to the diamond and two or more transition arrows pointing out from the diamond to indicate possible transitions from that point. Each transition arrow pointing out of a decision symbol has a guard condition. A merge symbol has two or more transition arrows pointing to the diamond and only one transition arrow pointing from the diamond, to ...