1. Types and Related Issues
Bindings

2. Bindings Are factors that characterize objects name location value
type
scope
lifetime

3. Bindings (continued) Can be static or dynamic
Can occur at many different times:
language design
operator symbols to operations
language implementation
range of values for integers
compile
variable to type
link
call to library subprogram
load
static variables to memory cells
run
value to variable

4. Names

5. Names Format Aliasing length character set case
reserved word or keyword for meaningful names in the language?
Aliasing

6. Location

7. Location Static Stack dynamic Explicit heap dynamic
Implicit heap dynamic
rare, used in APL and Algol-68

8. Type

9. Type Primitive or complex Usually bound statically Coercion or casting
but can be dynamic in LISP, APL, SNOBOL
Coercion or casting
Strong typing
language “always detects type errors”
Name compatibility or structure compatibility
name: same declaration or same type name
easier to implement but restrictive
structure: same internal structure
may not be strict enough

10. Type (continued)
Most languages use a combination of equivalence methods
Pascal: usually structure, but in some cases name is used (formal parameters)
C: structure, except for records
C++: name
Ada: restricted form of name
derived types allow types with the same structure to be different
type celcius is new real; type fahrenheit is new real;
subtype allows types to be compatible even with different names
subtype digit is INTEGER range 0..9;

11. Scope

12. Scope
Range of statements in a program when a name can be referenced (is visible)
Controlled by subprograms, compound statements
Static
most languages
Dynamic
APL, SNOBOL, some LISPs
means no compile-time type checking of non-local objects

13. Lifetime

14. Period when data object is allocated memory
Can be different than scope
hole in scope
static variables
invoking external subprogram