Computer science AQA A-level Paper 1

What is an integer?

A positive or negative whole number

What is a Real or Float number?

A positive or negative number that can have a fractional part.

What is a Boolean?

True or False

What is a character?

A single letter, number or symbol

What is a string?

A group of characters

What is Date/Time?

A way of storing Date/Time

What is a pointer?

A way of storing a memory address.

What is a record?

A collection of related fields, each of which could hold a different data type.

What is an array?

A finite, indexed set of related elements of the same data type.

What is a user defined data type?

A data type derived from existing data types in order to create a customized data structure.

What is variable declaration?

Creating a variable for the first time. giving it a name and sometimes a data type.

What is constant decleration?

Creating a constant for the first time.

What is assignment?

giving a constant or a variable a value.

what is iteration?

repetition of a process e.g. a while or for loop. this could be definite or indefinite.

What is selection?

comparing values and then choosing an appropriate action. e.g. an if statement.

what is a subroutine?

A named block of code containing a set of instructions designed to perform a frequently used operation.

What is definite iteration?

the number of repititions is known before the loop starts.

What is indefinite iteration?

the number of repititions is not known before the loop starts.

What is a nested structure?

One structure is placed within another. Easily identified by indentation.

What is meant by meaningful identifier names?

Giving constants, variables and subroutines sensible and meaningful identifier names.

What does the real/float division operator do?

divides one number by the other.

What does the integer division operator do?

divides one number by the other but only returns the whole number part.

What does the modulo operator do?

returns the remainder of an integer division.

What does the exponentiation operator do?

raises one value to the power of another.

What does the rounding operator do?

limits the degree of accuracy of a number. (rounds up or down)

What does the truncation operator do?

removes the decimal part of a number. (never rounds up)

what does the string handling function "Length" do?

Returns the number of characters in a specified string.

what does the string handling function "position" do?

returns the position of a specified character within a string.

what does the string handling function "concatenation" do?

joins two or more strings together to form a new and longer string.

Is a function required to return a value?

yes

is a procedure required to return a value?

no

what can stack frames store for each subroutine?

Return addresses

Parameters

Local variables

what is a recursive subroutine?

a subroutine defined in terms of itself.

what two conditions must a recursive subroutine meet in order for the program to run correctly.

it must have a stopping condition/base case.

this stopping condition must be met at some point.

what type of error would occur if a base case in a recursive subroutine is never met.

Stack overflow error.

what is a data type?

a particular kind of data item, as defined by the values it can take, the programming language used, or the operations that can be performed on it.

why is it important to give meaningful identifier names?

It allows a different programmer to work out the purpose of a constant, variable or subroutine from its name.

what two things are data types defined by?

there values they can take and the operations that can be performed on them.

is -44 an integer?

yes

which data type can only be true or false?

Boolean.

in what type of iteration is the number of repititions required not known before the loop starts?

Indefinite iteration

what visible feature of program code signifies nesting?

indentation.

using INTEGER division what is 14 DIV 3

4

using the modulo operation what is 30 MOD 4?

2

What is 1 XOR 1?

0

Name two advantages of using constants over hard coded values.

Constants can be given identifier names, making the code easier to understand for humans.

When updating the code constants only need updating at one position in code.

what is a seed value used for?

generating random numbers.

what name is given to code run to handle an exception?

Catch block

What name is given to a subroutine that always returns a value?

A function.

what are parameters used for?

to pass data values into a subroutine.

What name is given to the the actual value passed by a parameter?

An argument.

What type of variable can be passed from any part of the program?

Global variable

Name 3 items stored in a stack frame.

return address

parameters

local variables

what is meant by a recursive subroutine.

a subroutine defined in terms of itself.

what is meant by a base case.

the terminating situation in recursion. it does not use recursion to produce a result.

what scope is a variable that can be accessed from all parts of a program?

global scope

list 4 types of basic structure used in the structured approach to program design and construction.

Assignment

sequence

selection

iteration

what do rectangles represent in hierarchy charts?

procedures

how is data stored in procedural programs?

Constants and variables.

what name is given to containers for data and instructions In object oriented programming?

Objects.

in object-oriented programming, what specifies the properties and methods that objects have?

Classes

in class diagrams which type of line represents aggregation?

unfilled diamond.

in class diagrams which type of line represents composition?

filled diamond.

what are data structures

containers within which information is stored by computers.

what three things must an array be.

Finite

indexed

only hold elements of same data type.

to represent a table what type of array would you use?

a 2-dimensional array.

what is an abstract data type/data structure?

a data structure that makes use of other data structures to form a new way of storing data.

what is a queue?

an abstract data structure based on an array. A FIFO (first in first out) abstract data type.

an example of where queues are used in computer systems?

keyboard buffers, each key press is added to the queue.

which search algorithm uses a queue to keep track of which nodes have been visited?

breadth first.

what abstract data structure does a breadth first search algorithm use to keep track of which nodes have been visited?

A queue

how many pointers does a linear queue have?

2

where are the pointers located in a linear queue?

front and rear of the queue.

what operation adds a value into a queue?

enqueue

what operation removes a value into a queue?

dequeue

when a value is enqueued into a queue where is it entered?

at the rear.

when a value is dequeued from a queue where is it removed from?

the front.

what are the 4 operations that can be performed to a queue?

enqueue

dequeue

isfull

isempty

if a queue has no content what does the operation isfull return for that queue?

false

if a queue has no content what does the operation isempty return for that queue?

true

if a queue has no available positions behind the front pointer what does the operation isfull return for that queue?

true

if a queue has available positions behind the front pointer what does the operation isfull return for that queue?

false

how is emptiness detected in a queue?

if the front and rear pointer are at the same position the queue is empty.

what is an advantage to a circular queue?

more memory efficient.

what is the difference between circular and linear queues?

in a circular queue the front and rear pointers can move over the two ends of the queue.

how does a priority queue work?

items are assigned a priority, items with the highest priority are dequeued first.