Chapter 6

Question 1

What is a data type?

Answer 1

A collection of data values and a set of predefined operations on those values.

Question 2

What is a variable’s descriptor?

Answer 2

A collection of attributes.

Question 3

What is a primitive data type?

Answer 3

Built-in data types.

Question 4

What are some examples of primitive data types?

Answer 4

Integers, floating point, complex (FORTRAN, Python), decimal, boolean, and char

Question 5

How are these primitive data types stored or represented? Non-aggregate. ints, floats, chars, etc.

Answer 5

As a string of bits in memory.

Question 6

For character/string data types, what are the major design issues?

Answer 6

-Should they be static or dynamic?
-Are they built-in or not?
-What operations are allowed?
-How to store the string?
-How can we store dynamic strings?
-How to indicate length?

Question 7

What is an array?

Answer 7

A contiguous chunk of memory of the same data type.

Question 8

What are the design issues associated with arrays?

Answer 8

-What are the legal indices?
-Are accesses range-checked?
-When does a range for an array get bound?
-When is the memory allocated?
-Can multidimensional arrays be jagged? Rectangular? Both?
-Can you slice an array?

Question 9

What is a rectangular array?

Answer 9

A multidimensioned array in which all of the rows have the same number of elements and all of the columns have the same number of elements.

Question 10

What is a jagged array?

Answer 10

An array where the lengths of the rows need not be the same.

Question 11

What is a slice of an array?

Answer 11

Some substructure of that array

Question 12

What is an associative array? How is this different than a regular array?

Answer 12

An unordered collection of data elements that are indexed by an equal number of values called keys. Keys need to be stored in the structure, which differs from regular arrays.

Question 13

What is a record type?

Answer 13

An aggregate of data elements in which the individual elements are identified by names and accessed through offsets from the beginning of the structure.

Question 14

How do various languages implement records? For example, how does C implement a record?

Answer 14

C, C++, C#, and Swift: structs

Question 15

What is a tuple?

Answer 15

A collection which is ordered and unchangeable. Similar to records, but the elements are unnamed.

Question 16

What is a list?

Answer 16

An ordered collection.

Question 17

What is a pointer?

Answer 17

A variable that points to a memory location.

Question 18

What are the major design issues when dealing with pointers?

Answer 18

-What are the scope and lifetime of a pointer variable?
-What is the lifetime of a heap-dynamic variable (the value a pointer
references)?
-Are pointers restricted as to the type of value to which they can point?
-Are pointers used for dynamic storage management, indirect addressing,
or both?
-Should the language support pointer types, reference types, or both?

Question 19

What is a dangling pointer?

Answer 19

A pointer that lost its target.

Question 20

What is a lost pointer?

Answer 20

A pointer that is no longer accessible to the user program.

Question 21

What are solutions to dangling pointers and lost pointers?

Answer 21

-Dangling pointer: Assign pointer to null
-Lost pointer: Deallocate memory before termination of the program

Question 22

What is type checking?

Answer 22

Ensuring that the operands of an operator are of compatible types.

Question 23

What languages enforce type checking?

Answer 23

C, C++, Java, JavaScript, PHP

Question 24

What languages don’t enforce type checking?

Answer 24

Smalltalk, Ruby, Python

Question 25

What is strong typing?

Answer 25

A programming language is strongly typed if type errors are always detected.

Question 26

What is type equivalence?

Answer 26

Two types are equivalent if an operand of one type in an expression can be substituted for one of the other type, without coercion.