Lecture 4

Question 1

What are variables in programming?

Answer 1

Variables are abstractions in a language for the memory cells of a machine.

Question 2

What are the main attributes of a variable?

Answer 2

Type, Scope, Lifetime.

Question 3

What are names associated with in programming?

Answer 3

Names are associated with subprograms, formal parameters, and other program constructs.

Question 4

What is an Identifier?

Answer 4

Identifier is another term for a name.

Question 5

What are some design issues for names?

Answer 5

Whether names are case sensitive and whether special words are reserved words or keywords.

Question 6

What are the forms of names(name forms) in programming languages?

Answer 6

Names are strings of characters used to identify entities in a program, with different length limitations and naming conventions depending on the language.

Question 7

What are common naming conventions?

Answer 7

Underscore characters and Camel notation.

Question 8

What is the controversy around case sensitivity in programming languages?

Answer 8

Some believe it detracts from readability, while others do not see it as a problem.

Question 9

What are special words in programming languages used for?

Answer 9

To make programs more readable and to separate syntactic parts of statements and programs.

Question 10

What is the difference between a keyword and a reserved word?

Answer 10

A keyword is special only in certain contexts, while a reserved word cannot be used as a name.

Question 11

What attributes characterize a variable?

Answer 11

Name, address, type, lifetime, and scope.

Question 12

What is the address of a variable?

Answer 12

The machine memory address associated with the variable.

Question 13

What are aliases?

Answer 13

When more than one variable name can access the same memory location.

Question 14

What does the type of a variable determine?

Answer 14

The type determines the set of values the variable can store and the operations that can be performed on those values.

Question 15

What is the value of a variable?

Answer 15

The contents of the memory cell(s) associated with the variable.

Question 16

What is binding in programming?

Answer 16

The association between an attribute and an entity.

Question 17

When can binding occur?

Answer 17

Language design time, implementation time, compile time, load time, link time, and run time.

Question 18

What is static binding?

Answer 18

Binding that occurs before run time and remains unchanged during program execution.

Question 19

What is dynamic binding?

Answer 19

Binding that occurs during run time or can change during program execution.

Question 20

What must happen before a variable can be referenced in a program?

Answer 20

It must be bound to a data type.

Question 21

What are explicit and implicit declarations in static type binding?

Answer 21

Explicit declaration specifies variable names and types; implicit declaration uses default conventions to associate variables with types.

Question 22

What is dynamic type binding?

Answer 22

The type of a variable is bound when it is assigned a value in an assignment statement.

Question 23

What is an advantage of dynamic type binding?

Answer 23

Provides more programming flexibility.

Question 24

What is a disadvantage of dynamic type binding?

Answer 24

It diminishes the error-detection capability of the compiler and requires run-time type checking.

Question 25

What is allocation in the context of storage bindings?

Answer 25

The process of taking memory cells from a pool of available memory.

Question 26

What is deallocation?

Answer 26

Returning a memory cell to the pool of available memory after it is unbound from a variable.

Question 27

What is the lifetime of a variable?

Answer 27

The time during which a variable is bound to a specific memory location.

Question 28

What are static variables?

Answer 28

Variables bound to memory cells before program execution begins and remain bound until program termination.

Question 29

What are stack-dynamic variables?

Answer 29

Variables whose storage bindings are created when their declaration statements are elaborated during run time.

Question 30

What is an advantage of implicit heap-dynamic variables?

Answer 30

High flexibility and the ability to write highly generic code.

Question 30

What are explicit heap-dynamic variables?

Answer 30

Nameless memory cells allocated and deallocated by explicit run-time instructions, referenced through pointers or reference variables.

Question 31

What are implicit heap-dynamic variables?

Answer 31

Variables bound to heap storage only when assigned values, with all attributes bound at each assignment.

Question 32

What is a disadvantage of implicit heap-dynamic variables?

Answer 32

Run-time overhead for maintaining dynamic attributes and loss of some compiler error detection.

Question 33

In what way are reserved words better than keywords?

Answer 33

Compile time, load time, link time, and run time.

Question 34

Define binding and binding time.

Answer 34

Binding is the association between an attribute and an entity, and binding time is when this association occurs.