PLC

Question 1

What does the process of allocation to a variable do?

Answer 1

To allocate a variable is to bind an address to it

Question 2

What does it mean if the process of allocation is done dynamically

Answer 2

If allocation is done dynamically then it is done during the runtime

Question 3

What does it mean if the process of allocation is done statically

Answer 3

If allocation is done statically then it is done during initialisation time

Question 4

What are the 6 attributes of variables

Answer 4

Name
Address (aka L-Value)
Value (aka R-Value)
Type
Extent
Scope

Question 5

What are the two types of binding

What do they each mean

Answer 5

Static and Dynamic

Static binding means that variables are bound during compile time and do not change during execution

Dynamic binding means they either: are bound for the first time at runtime or a binding changes during runtime

Question 6

What is the extent of a variable

Answer 6

The extent is the time between allocation and deallocation

Question 7

What are the four kinds of variables

Answer 7

Static Variables
Stack dynamic variables
Explicit heap dynamic variables
Implicit heap dynamic variables

Question 8

Explain what Static Variables are

Answer 8

Also known as global variables these are bound to a memory at initialisation time. An example of these are static class variables in Java

Question 9

Explain what Stack Dynamic Variables are

Answer 9

Also known as local variables the memory for these is allocated from the runtime stack when some declaration, i.e. a method, is executed. These are deallocated when that procedural block they are used in returns. An example of a stack dynamic variable is the local variables in a method declaration

Question 10

Explain what Explicit heap dynamic Variables are

Answer 10

These are nameless, abstract memory locations which can be allocated and deallocated by the programmer using explicit command such as malloc in C or new in Java

Question 11

Explain what Implicit Heap Dynamic Variables are

Answer 11

These are an error prone and inefficient form of variable which memory is allocated to when the variables are assigned to values, it is deallocated and reallocated when the variable is redefined

Question 12

What are the two types of type binding?

Answer 12

Static type and dynamic type binding

Question 13

What are the two types of static type binding

Answer 13

Type declaration and type inference

Question 14

What is static type, type declaration, binding

Answer 14

Then name when variables are introduced with an explicit type (and possibly value)

Question 15

What is static type, type inference, binding

Answer 15

Then name for when variables types are worked out from usage of the variable or by following a fixed naming scheme

Question 16

What is dynamic type binding

Answer 16

The name given when variable are assigned a type at runtime the variables type’s is allowed to change during execution should it be assigned a variable of another type.

Question 17

What is the Extent of static variables

Answer 17

The whole program

Question 18

What is the Extent of Static Dynamic Variables

Answer 18

A particular stack frame or procedure call

Question 19

What is the extent of explicit heap dynamic variables

Answer 19

Explicit allocation to explicit deallocation

Question 20

What is the extent of Implicit heap dynamic variables

Answer 20

Implicit allocation to implicit deallocation