We start with empty

• symbol table and
• memory.

int a;

is a declaration statement. It declares that variable a is of type int.

It causes a number of actions:

• a new entry in symbol table for variable a
  • note that the type is int
• a new entry in memory for variable a
  • note that the content is uninitialized at this point. It is indicated by ?.

a = 4;

is an assignment statement. It changes the value of a variable, which is already defined.

• sets the content of memory location of a to 4.

int b = 5;

has the same effect of

int b;
b = 5;

It causes both declaration and initialization:

• a new entry in symbol table for variable b
  • note that the type is int
• a new entry in memory for variable b
• sets the content of memory location of b to 5.

int c = 7;

is not any different than int b = 5;.

We will focus on variable c little bit more.

c = 8;

sets the content of c to 8.

Isn't it similar to a = 4?

Note that

c = a;

is little tricky. It means take the content of a put into c.

So does this:

c = 9;

It changes the content of c once more. Now it becomes 9.

double d;

is a declaration statement. It declares that variable d is of type double.

It causes a number of actions:

• a new entry in symbol table for variable d
  • note that the type is double
• a new entry in memory for variable d
  • note that the content is uninitialized at this point. It is indicated by ?.

d = 1.2;

is an assignment statement. It changes the value of a variable, which is already defined.

• sets the content of memory location of d to 1.2.

d = a;

is another assignment statement similar to c = a. But there is a very important difference.

• In c = a, both a and c were of type int.
• In d = a;, there is a type mismatch.
• The content of d becomes 4.

This is similar to the previous statement.

a = d;

• we again have type mismatch.
• The current value of d is 4. So we do not expect any problem.