Methods - Multimedia Introduction to Programming Using Java - page 93

• Program counter. The program counter is the number of the next state-
ment of the method body to execute. Initially, it is 1, and it is increment-
ed each time a statement is executed.
• Scope box. The scope box is used to find a variable or method that is ref-
erenced in the method body. Its value depends on what kind of method
this is:
for a static method : The name of the class in which the
method is defined.
for an instance method : The name of the object in which
the method resides.
for a constructor : The name of the object that was just created.
• Parameters. Each parameter of the method appears as a variable.
Parameters are drawn in the lower left of the frame for reasons that will
become clear later.
• Local variables. Each local variable of the method appears in the frame.
As an example, consider this class:

public class C {
public void meth( int p) {
double d;
…

}

}
Suppose we execute these statements:

C c= new C();
c.meth(5);
Execution of the first statement creates a new folder, stores its name in vari-
able c , and calls procedure c.meth . Figure 2.9 shows variable c , the folder, and
the frame for the method call c.meth just after the frame is created and the argu-
ment is stored in the parameter.

The call stack: the stack of frames for uncompleted method calls
A frame for a method call lasts as long as the method call is being executed.
When the call is finished, the frame is erased. If the method is called again later,
a new frame is created for it.

a1

meth : 1 a1

C

c

a1

y

p

5

d

meth( int )

Figure 2.9: The frame just after the argument has been assigned to parameter p