Chapter 20

Question 1

low-level programming

Answer 1

programming which gives instructions directly to the computer’s hardware

used for maximum efficiency and speed. an example of low-level is assembly language

Question 2

addressing modes

Answer 2

immediate = the value of the operand is used in the instruction (no reference to memory)

direct = the operand is the memory address which holds the value to be used

indirect = the operand is a memory address which holds another memory address where the value to be used is

indexed = the operand contains a value that must be added with the IX, to produce the address where the instruction to be executed is

relative = the operand forms the distance of the value’s instruction (combined with the PC or IX) from the address of the current instruction

Question 3

symbolic and absolute addresses

Answer 3

symbolic addresses = contains a symbolic name for the address it represents
absolute addresses = the numeric address of a memory location. restrictive - program cannot be loaded anywhere else in memory

Question 4

imperative programming

Answer 4

describes step by step the commands the computer should follow to complete a task in the order it was given
- is an imperative sequence of statements
- use variables which are changed using assignment statements
- use variables, loops, conditional statements
an example of this is python or java

Question 5

object-oriented programming (OOP)

Answer 5

organizes code into objects. translates real world into code.
Python and Java are object-oriented.

Question 6

advantage of OOP over imperative

Answer 6

produces robust, more reliable code
attributes can only be manipulated using methods from the class, protecting from accidental change.

Question 7

objects

Answer 7

an instance of a class

Question 8

create an object (pseudocode)

Answer 8

objectName <- NEW className(<param></param>, <param1>, ...)</param1>

Question 9

class

Answer 9

a template for objects.

a data structure that is created by the programmer and has its own attributes and methods which operate on the class.

Question 10

declare a class in OOP pseudocode

Answer 10

CLASS class
     PRIVATE attribute : DATATYPE
     PUBLIC PROCEDURE NEW(Givenattribute : DATATYPE)
          attribute <- Givenattribute
     ENDPROCEDURE
     PRIVATE attribute1 : DATATYPE
     attribute1 <- value
     PRIVATE FUNCTION GetAttribute1() RETURNS DATATYPE
          RETURN attribute1
     ENDFUNCTION
ENDCLASS

first procedure is to set the attribute, the function is to return the value of the attribute
methods and properties are assumed to public unless otherwise stated.
new and getattribute1 are just names, all of the names here can be changed

Question 11

why are attributes private? are methods public?

Answer 11

• so that only that class has direct access to the variable - everything else needs a method to change/access the data.
• to ensure attributes can only be accessed by the class’s own methods
• to enforce encapsulation//to protect them

yes, methods are public, due to the aforementioned reasons.

Question 12

properties/attributes

Answer 12

data stored about an object defined in a class

Question 13

methods

Answer 13

subroutines in an object operating on the data

the procedures in a class implementing the behaviours that act on the properties/attributes

Question 14

inheritance

Answer 14

allows a new class to inherit the properties and methods of an existing class

the child/subclass has access to all the attributes and methods of the parent/base/superclass, along with having their own attributes and methods.

Question 15

inheritance in pseudocode

Answer 15

CLASS childClass INHERITS parentClass

Question 16

polymorphism

Answer 16

when a method behaves differently for different classes in the hierarchy

Question 17

containment

Answer 17

when a class contains other classes
(one class contains another class type)

Question 18

encapsulation

Answer 18

putting properties and methods inside a class (to hide sensitive data from users)

Question 19

abstraction

Answer 19

hiding the complex programming and only showing what is necessary

Question 20

getters

Answer 20

a getter is used to access/return the value of an attribute

Question 21

setters

Answer 21

a setter is used to update the value of an attribute/property

Question 22

what does protected mean?

Answer 22

a class and subclass can access a variable, but not any other classes, which must use getters or setters

Question 23

instance

Answer 23

an occurrence of an object//an instantiation of a class

Question 24

declarative programming

Answer 24

programmer describes the desired output and rather than how to do it
… using facts and rules
… using queries to satisfy goals.
Can be logical or functional
Logical - states a program as a set of logical relations
Functional – constructed by applying functions to arguments / uses a mathematical style

examples are SQL and Prolog

Question 25

prolog rules

Answer 25

these are more explanatory than mark-scheme founded
goal = finds the data from the written information that fufills your condition
* studies(Student, history).
* variables are capitalized, nothing else
rule = establishes relationships between variables using an if (:-) operator
query = written in the query window to find an answer from the given data (returns true or false). example:
* ? - likes(john, jane).

Question 26

queries

Answer 26

goals stated by the user that the language uses to solve a problem

Question 27

prolog rules

Answer 27

instantiation:
vegetable(cucumber). #means cucumber is a vegetable,
full stops follow all statements

:- means IF
, means AND

Question 28

exception handling

Answer 28

the process of responding to an unexpected event when the program is running so it does not halt unexpectedly

programming errors, user errors, hardware failure, runtime errors

Question 29

why should you include exception handling routines when writing a program? examples of exceptions?

Answer 29

• to trap runtime errors
• to prevent a program from halting unexpectedly
• to produce meaningful error messages
• e.g. (run-time): dividing by zero, end of file, file not found

Question 30

open a file (not random)

Answer 30

OPENFILE “fileName” FOR MODE
#modes are read, write, append

Question 31

read from a file (in read mode)

Answer 31

READFILE “fileName”, variableName

Question 32

test if there are any more lines in the file:

Answer 32

EOF(“fileName”)

Question 33

write data into a file (WRITE or APPEND mode)

Answer 33

WRITEFILE “fileName”, data
#data can be a variable, a string (held in quotations), etc.

Question 34

close a file

Answer 34

CLOSEFILE “fileName”

Question 35

random file pseudocode commands:

Answer 35

OPENFILE “fileName” FOR RANDOM

SEEK “fileName”, address
#moves the file pointer to a given location, address can be a variable

GETRECORD “fileName”, variable
#used to read a record at the file pointer, inserts the record read into the variable

PUTRECORD “fileName”, variable
#writes a record into the file at the file pointer, data in the variable is inserted into the location in the file

EOF(fileName) and CLOSEFILE fileName