Objects can change states in response to events or over time. A UML state diagram captures these state changes by showing the possible states of an object, the transitions between states, and the starting and ending points of state change sequences. It also models the entry and exit activities that occur when a system enters or leaves a state, as well as activities that occur within a state. Guard conditions can be used to specify when a transition takes place.

2. •One way to characterize change in a system is to
say that its object change their state in response
to events and to time .
• When you throw a stick a light changes its state
from off to on .
•When you click a remote control a television
changes its state from showing you one
channel to showing you another .
• After an appropriate amount of time , a
washing machine changes its state from Washing
to Rinsing .

3. •The uml state diagram captures
these kind of changes .It presents the
states an object can be in along with
the transitions between the states
and shows the starting point and
end point of a sequence of state
changes.

8. •Three frequently used activities are entry(what
happens when the system enters a state)
,exit(what happens when the system leaves the
state ) and what happens while the system is in the
state.
•You can add others as necessary.

11. Guard condition is something
when its met transition take
place

12. Here the Screensaving is a guard condition.