CH16

Question 1

describe the purpose of a user-defined data type (2)

Answer 1

it allows programmers to create new data types from existing data types and helps to extend the flexibility of the programming language

Question 2

explain the reason why binary numbers are stored in normalized form (3)

Answer 2

1. to store the maximum range of numbers in the minimum number of bytes

2.enables very large numbers to stored with accuracy

3.avoids the possibility of many numbers having multiple representations

Question 3

explain what is meant by a user-defined composite data type. Include an example (3)

Answer 3

its a data type that is constructed by a programmer and references at least one other data type, the data types can be primitive or user defined. E.g: A class

Question 4

explain why certain properties are set to private in programs (2)

Answer 4

• to ensure they’re hidden
• to ensure that attributes can only be accessed by the Class’s own methods

Question 5

what is meant by an enumerated data type

Answer 5

a user-defined non composite data type with an ordered list of possible values

Question 6

what is meant by the term pointer data type

Answer 6

a user-defined non composite data type that’s used to reference a memory location

Question 7

state when underflow occurs in a binary floating-point system (2)

Answer 7

when following a logical operation and the result is too small to be precisely represented in the available system

Question 8

explain why a binary representation is sometimes only an approximation to the real number it represents (3)

Answer 8

1- real numbers can have a fractional part such as 1/2
2-the fixed length of storage means that you can’t store very large numbers
3- binary numbers represent numbers based on the powers of 2 with limited fractional representations such as 1/2, 1/4, 1/8

Question 9

describe what is meant by a composite data type (2)

Answer 9

a user-defined data type that is a collection of data that can consist of multiple elements of different data types

Question 10

describe what is meant by non-composite data type (2)

Answer 10

I can be defined without referencing another data type, it can be a user defined data type

Question 11

outline what is meant by the term collision (2)

Answer 11

a collision is when 2 values pass through a hashing algorithm and result in the same hash value, this is an issues because 2 records cannot occupy the same address

Question 12

explain how a collision can be dealt with when writing records to a random file (3)

Answer 12

1- a process of collision resolution is used
2- start at the original hashed storage space
3- go through the following spaces in a linear fashion