Module 3: Basic Semantics and Pointer Semantics

Question 1

What is semantics concerned with?

Answer 1

Semantics is concerned with what the parse tree means.

Question 2

What are the properties that we want from language semantics definitions? (Select all that apply)

a. Preciseness
b. Acceptability
c. Predictability
d. Complete

Answer 2

a. Preciseness
c. Predictability
d. Complete

Question 3

What are the ways that language semantics can be specified?

a. English specification
b. Reference implementation
c. Formal Language
d. All of the above

Answer 3

d. All of the above

Question 4

Given the line of code below, is this an explicit or implicit declaration?

int i;

Answer 4

This is an explicit declaration. We are saying that i is that name of the variable explicitly

Question 5

What does the following represent?

target = test_value + 10

a. explicit declaration
b. implicit declaration

Answer 5

b. implicit declaration

Question 6

What does scope cover in semantics?

a. How long is the name valid?
b. How to resolve the name?
c. What is the name?
d. What declaration is the name mapped to

Answer 6

a. How long is it valid
b. How to resolve the name
d. What declaration is the name mapped to

Question 7

What kind of scoping does the C programming language use?

a. Block-level
b. Function-level
c. None

Answer 7

a. Block-level

Question 8

What is used to map the name to the declaration in scoping?

a. Variable table
b. Nothing
c. Declaration table
d. Symbol table

Answer 8

d. Symbol table

Question 9

What are the two types of scoping?

Answer 9

a. Static Scoping

b. Dynamic Scoping

Question 10

How can function calls be resolved to appropriate functions?

a. Names
b. Names + return type?
c. Names + parameter number?
d. Names + parameter number + parameter types
e. All of the above

Answer 10

e. All of the above

Question 11

Using a box and circle diagram what does the x represent?

a. Name
b. Binding
c. Location
d. Value

Answer 11

a. Name

Question 12

Using a box and circle diagram what does the box represent?

a. Name
b. Binding
c. Location
d. Value

Answer 12

c. Location

Question 13

Using a box and circle diagram what does the circle represent?

a. Name
b. Binding
c. Location
d. Value

Answer 13

d. Value

Question 14

Using a box and circle diagram what does the line represent?

a. Name
b. Binding
c. Location
d. Value

Answer 14

b. Binding

Question 15

What are the two operations with pointers?

Answer 15

The address operator (&) and the deference operator (*)

Question 16

True or False: The & operator is a unary operator and can only be applied on an L value.

Answer 16

True.

This means that it can only be applied once and can not be applied on something like
&b
but not
&(b+c)

Question 17

What is the return value of &?

a. l-value
b. r-value

Answer 17

b. r-value of type T*

For example:
&x -> int*
this would take the address of x and turn it into an int

Question 18

True or False:

The difference operator can only be applied to l-values

Answer 18

False.

The difference operator can be applied to both l-value and r-value operators.

Question 19

If x is of type T* what does the box and circle diagram look like?

Answer 19

It gives the typical box diagram of X with Xv inside of the circle. If we call *X we take the address of Xv and find the location that has that address Xv. *X will get the value V from the address and return it. V has to be of type T for it to work.

Question 20

What type of return value does *X return?

a. l-value
b. r-value

Answer 20

a. l-value

Question 21

What memory does the malloc operation send values to?

a. global
b. heap
c. stack

Answer 21

b. heap

Question 22

True or False:

Every malloc results in a new location in the heap.

Answer 22

True

Every malloc does result in a new location in the heap

Question 23

What does malloc return?

Answer 23

Malloc will return the address of the value.

Question 24

What does *x mean?

Answer 24

Take the value of inside X, go to that address and return the value of that address. This is type of link.

Question 25

What is an alias?

Answer 25

Alias is when variables are associated with the same locations.

Question 26

How can you create new locations and reserve the associated address? a. Find the address and make it the address b. Finding memory that is not currently reserved c. Associate that memory with a variable name or reserving the memory and returning the address of the memory d. All of the above

Answer 26

b. Finding memory that is not currently reserved | c. Associate that memory with a variable name or reserving the memory and returning the address of the memory

Question 27

What is memory deallocation?

Answer 27

Memory deallocation is the process of how to release locations and associated addresses so that they may be reused later in program execution.

Question 28

What are the types of memory allocation? a. Global allocation b. Stack allocation c. Variable allocation d. Heap allocation

Answer 28

a. Global allocation b. Stack allocation d. Heap allocation

Question 29

True or False: | Global memory is never deallocated.

Answer 29

True, global memory is allocated once and the allocated memory is not deallocated

Question 30

Which of the following best explains stack allocation? a. It is allocated once and is not deallocated after b. It is allocated with nested scopes and function calls, the memory reserved is automatically deallocated when out of scope c. Allocation is explicitly requested by the program d. It

Answer 30

b. It is allocated with nested scopes and function calls, the memory reserved is automatically deallocated when out of scope

Question 31

Explain heap allocation

Answer 31

Allocation is explicitly requested by the program (malloc and new) and has to be deallocated by calling things like free.

Question 32

What are the two types of memory errors?

Answer 32

a. Dangling Reference | b. Garbage

Question 33

What is a dangling reference error? a. Reference to a memory address that was originally allocated but is now deallocated. b. Reference to a memory address that has been deallocated but is now allocated c. Memory that has been allocated in the heap and has not been explicitly deallocated, yet is not accessible by the program

Answer 33

a. Reference to a memory address that was originally allocated but is now deallocated

Question 34

What is a garbage memory error? a. Reference to a memory address that was originally allocated but is now deallocated. b. Reference to a memory address that has been deallocated but is now allocated c. Memory that has been allocated in the heap and has not been explicitly deallocated, yet is not accessible by the program d. Memory that has been allocated in the stack and has not been explicitly deallocated, yet is not accessible by the program.

Answer 34

c. Memory that has been allocated in the heap and has not been explicitly deallocated, yet is not accessible by the program

Question 35

What is a common outcome of having a memory error?

Answer 35

A segmentation fault