CSC 351 - Chapter 6

Question 1

data type

Answer 1

defines a collection of values and a set of predefined operations on those values.

Question 2

user-defined types

Answer 2

improved readability by using meaningful names and allow changeability

Question 3

abstract data type

Answer 3

the interface of a type is separated from the representation and set of operations on values of the type

Question 4

descriptor

Answer 4

collection of the attributes of a variable

Question 5

primitive data types

Answer 5

data types that are not defined in terms of other types

numeric types - floating point, integer, complex, decimal, boolean, character

Question 6

character string type

Answer 6

values consist of sequences of characters. Character string constants are used to label output, and the input and output of all kinds are often done in terms of strings.

Question 7

character string type design issues

Answer 7

• should strings be a special kind of character array or a primitive type
• should strings have static or dynamic length

Question 8

string operations

Answer 8

assignment, catenation, substring reference, comparison and pattern matching

Question 9

static length string

Answer 9

length is static and set when the string is created

Question 10

limited dynamic length string

Answer 10

allow strings to have varying length up to a declared and fixed maximum set by the variables definition

Question 11

dynamic length string

Answer 11

allow strings to have varying length with no maximum

Question 12

ordinal type

Answer 12

the range of possible values can easily be associated with the set of positive integers

Question 13

user-defined ordinal types

Answer 13

• enumeration

- subrange

Question 14

enumeration types

Answer 14

possible values are provided in the definition. they provide a way of defining and grouping collections of named constants. they can enhance readability and reliability.

Question 15

subrange types

Answer 15

a contiguous subsequence of an ordinal type. can enhance readability and reliability

Question 16

array types

Answer 16

homogeneous aggregate of data elements in which an individual element is identified by its position. the individual data elements are of the same type.

Question 17

static array

Answer 17

subscript ranges are statically bound and storage allocation is done before run time. this is efficient but the storage size is fixed.

Question 18

fixed stack-dynamic array

Answer 18

subscript ranges are statically bound and storage allocation is done during execution. this is space efficient

Question 19

stack-dynamic array

Answer 19

both the subscript ranges and storage allocation are dynamically bound during execution. these are flexible but once subscript ranges are bound they are fixed

Question 20

fixed heap-dynamic array

Answer 20

subscript ranges and the storage binding are both fixed after storage is allocated. these are flexible, but the allocation time is longer because it is using the heap rather than the stack

Question 21

heap-dynamic array

Answer 21

binding of subscript ranges and storage allocation is dynamic and can change any number of times during the arrays lifetime. these are flexible but not time efficient

Question 22

slice

Answer 22

some substructure of an array

Question 23

associative array

Answer 23

unordered collection of data elements that are indexed by an equal number of values called keys (hashes, dictionaries, maps)

Question 24

record types

Answer 24

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

Question 25

tuple types

Answer 25

similar to a record except that the elements are not named

Question 26

union type

Answer 26

variables may store different type values at different times during program execution

Question 27

pointer type

Answer 27

variables have a range of values that consist of memory addresses and a special value, nil. pointers provide indirect addressing and a way to manage dynamic storage

Question 28

reference type

Answer 28

refers to an object or value in memory.

Question 29

decimal type adv/disadv

Answer 29

adv: able to precisely store decimal values which cannot be done with floating-point. disadv: the range of values are restricted because no exponents are allowed

Question 30

array design issues

Answer 30

- what types are legal for subscripts? - are subscripting expressions in element references range checked? - when are subscript ranges bound - when does array allocation take place - can arrays be initialized when they have their storage allocated - what kind of slices are allowed

Question 31

column major order

Answer 31

the elements of an array that have the lower bound value stored in the last subscript are stored first

Question 32

row major order

Answer 32

elements of an array that have the lower bound value of stored in the first subscript are stored first

Question 33

fully qualified reference to record fields

Answer 33

all intermediate record names are named in the reference

Question 34

elliptical references to record fields

Answer 34

the field is named, but any of the enclosing record names can be omitted as long as the reference is unambiguous

Question 35

union design issues

Answer 35

- should type checking be required? | - should unions be embedded in records?

Question 36

free unions

Answer 36

programmers are allowed complete freedom from type checking in their use

Question 37

discriminated union

Answer 37

each union construct is required to include a type indicator called a discriminant. a union with a discriminant is a discriminated union.

Question 38

design issues for pointers

Answer 38

- what is the scope and lifetime of a pointer variable? - what is the lifetime of a heap-dynamic variable? - are pointers used for dynamic storage management and/or indirect addressing

Question 39

dangling pointer

Answer 39

pointer that contains the address of a heap-dynamic variable that has been deallocated

Question 40

compatible type

Answer 40

is legal for the operator or is allowed under language rules to be implicitly converted by compiler generated code

Question 41

type error

Answer 41

application of an operator to an operand of an inappropriate type

Question 42

strongly typed

Answer 42

type errors are always detected

Question 43

type name equivalence

Answer 43

two variables have the same type if they are defined in the same declaration or in declarations that use the same type name. easy to implement but more restrictive.

Question 44

structure type equivalence

Answer 44

two variables have the same type if their types have identical structures. more flexible but more difficult to implement

Question 45

nonconverting cast

Answer 45

the means of extracting the value of a variable of one type and using it as if it were of a different type