Contents Introduction Names Variables The Concept of Binding Type Checking Strong Typing Type Equivalence Scope Scope and Lifetime Referencing Environments Named Constants Introduction

Address

Address

• Meaning: the memory address with which it is associated
• The same name may be associated with different addresses at different places and at different times in the program
• The same variable can be associated with

different addresses at different times during

program execution

• Attributes:

Type

Type

• Meaning: determines the range of values of variables and the set of operations that are defined for values of that type.
• Example: integer type in Java
• Range of values :-2,147,483,648 .. 2,147,483,647
• Set of Operations: +, -, *, Mod, Div

• Attributes:

int n;

703	704	705	706	707	708
	n

Value

Value

• Meaning: the contents of the location with which the variable is associated.
• The l-value of a variable is its address
• The r-value of a variable is its value

• Attributes:

Meaning: A binding is the association of data/code with an identifier

• Language design time : bind operator symbols to operations

(ex. * is bound to multiplication)

• Language implementation time: bind floating point type to a representation

(in java float represents as 4 bytes according to IEEE-754

• Compile time: bind a variable to a type in C or Java

(ex. int n  n is bound integer type at compilation )

4. Load time: bind a C or C++ static variable to a memory cell)

(i.e. allocate in memory)



5. Runtime: bind a non-static local variable to a memory cell.

(ex. object in Java; a value is bound to variable at runtime)

• Binding time is the time at which a binding takes place.

• Meaning: A binding is the association of data/code with an identifier


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