Review 2

1
Review 2
2
Binding

• What is binding?
• When does binding of names occur?
• What is a variable?

3
Binding and Attributes

• Name and describe 6 attributes that can be bound
  to a variable name?
• When does binding of names occur?
• What is an alias?

4
Three Memory areas

• The memory area allocated for a program's data is
  divided into 3 areas. What are their names?
• What kind of values are placed in each area?
• Name a language that allocates all storage in
  only one of these area?

5
Scope

• There are 2 types of scope rules. What are they
  called?
• Most languages use which type of scope?
• C

int x 10 int fun(int x) x x x return
x int main( ) int y x int x
fun(y) // what is x ? // what is y ?
6
Linking of names

• What is the name of the software that joins
  object files and resolves external references in
  object files?
• Does this program verify data types?

/ File 1 / char foo extern double
bar ... printf("s", foo) printf("f", bar)
/ File 2 / extern double foo char bar
"foo!" ... printf("d", foo) printf("s", bar)
7
Referencing environment

• What is a referencing environment?
• In the calculator, how do we store the
  referencing environment?
• Is the Symbol Table needed by the binary
  (executable) program?
• Is the symbol table included in the output of the
  linker (compiled program)?
• On Linux, how can you get rid of the symbol
  table?

8
Symbol Table

• What information is in the symbol table?
• Is the Symbol Table needed by the binary
  (executable) program?
• Is the symbol table included in the output of the
  linker (compiled program)?
• On Linux, how can you get rid of the symbol table
  in a binary (compiled) program file?

9
Remembering values

• I want to write a C function that tells me how
  many times the function has been called.

counter( ) // returns 1 counter( ) //
returns 2 counter( ) // returns 3 ...

• how can I write a counter() function that
  remembers how many times it has been called?
  (without using global variables)

int counter( ) static int count 0 return
count
10
Call By...

• What are the names of the 3 methods of passing
  parameters to subroutines?
• Describe each one.
• What language useswhich param passing
  method?Java, C, C, Fortran-77

int fun(int x) x x x return x int
main( ) int y 20 printf( fun(y)
) printf( y ) // what is printed?
11
Test the param passing method?

• Design a simple program to determine which
  parameter passing method is being used.

void fun( ) int main( )
12
Values versus References

• What is a value data type?
• What is a reference data type?

Integer fun(Integer x) x x x return
x int main( ) Integer x 10 Integer y
fun(x) // what is x ? // is (y x) ?
int fun(int x) x x x return x int
main( ) int x 10 int y fun(x) // what
is x ? // is (y x) ?
13
What does this do?
what does this do? sub(, List). sub(HT,
List) - member(H, List), sub(T, List).
14
What does this do?
Underscore (_) means "don't care". It accepts any
value.
what does this do? foo(, _, ). foo(HT,
List, HP) - member(H, List), foo(T, List,
P). foo(HT, List, P) - not( member(H, List)
), foo(T, List, P).
15
Memory and VMT
Person - name Person(name String) getName()
String

• Person kung new Foo("Kung",20)
• Draw a picture of the contents and layout of
  memory used by kung.
• Draw the VMT for Foo, showing methods in the
  correct order.
• Refactor
• how does the picture change if nextID is moved to
  the Person class?

Foo - nextID int - age int Foo( String,
int) getAge() inttoString() String