Data Types, Data Structures, Scope And Parameters

Question 1

What is a record?

Answer 1

A collection of data stored for one item, person or event. A record may contain data items of different data types

Question 2

What is a sequential file?

Answer 2

Data may be read from or written to external files. Data items are read/written in sequence. This is useful if the data is to be kept after program execution.

Question 3

What is a subroutine?

Answer 3

A block of code that has been separated from the main program, they usually perform a single task or action. The subroutine is called by another part of the program when required, the lines in the subroutine are then executed and the program continues from the call command.

Question 4

What is modular programming?

Answer 4

Aims to split a program into as many self-contained subroutines as possible. Modularity improves the maintainability of a program as it is possible to re write a single module without changes impacting on the rest of the program.

Question 5

What is the scope of a variable?

Answer 5

The area of a program in which the variable can be used. A variable may be declared as either global - has global scope - so can be used at any point in the code, - or local . A local variable can only be used - has scope - inside the subprogram where it is defined.

Question 6

What is an advantage of a local variable?

Answer 6

The value of a local variable can only be altered within the one part of the program in which it exists - has scope - usually a subroutine.

Question 7

Describe the difference between a data type and a data structure

Answer 7

A data type is used to store a single variable. A data structure is used to store multiple items of data.

Question 8

What is an array?

Answer 8

A type of data structure with numbered elements, each of element stores an item of the same data type

Question 8

What is a procedure?

Answer 8

A subroutine which performs a task that is contained completely within its code.

Question 9

What is a method?

Answer 9

A subroutine used in object-oriented programming that defines the behaviour of an object.

Question 10

What is a function?

Answer 10

A subroutine with code that calculates a value which it returns to the main program.

Question 11

What does passing a parameter by value mean?

Answer 11

If a variable is passed by value, a copy of the data is made within the subroutine. Any changes made to the passed data do not affect the original data.

Question 13

What does parameter passing by reference mean?

Answer 13

If a variable is passed by reference, the original data is used inside the subroutine - no copy is made. So the global / passed value gets modified within the subroutine.

Question 14

What is a formal parameter?

Answer 14

This refers to the variable name used on the subroutine definition line. Formal parameters only have a value when the subroutine is called. Example: procedure calc_wages hours rate

Question 15

What is an actual parameter?

Answer 15

This refers to the actual data values that are passed into the subroutine at run time, when the subroutine is called e.g. calc_wages 40 7.50

Question 16

What is the difference between a fixed loop and a conditional loop?

Answer 16

A fixed loop goes around a program a set number of times where as a conditional loop goes around until certain criteria are met.

Question 16

Concatenation

Answer 16

When two or more strings/substrings are joined

Question 17

What is a user defined function?

Answer 17

A user defined function is a function provided by the user to perform a specific task in order to generate a value.

Question 18

Value held by Boolean data types

Answer 18

A true or false value

Question 19

How is each element in a 1-D array identified?

Answer 19

An index value

Question 20

Sequential File

Answer 20

A file that holds data in a set order

Can be opened, closed, read from or written to

Question 21

What file operation is triggered if a non existent file name is opened?

Answer 21

Create

Question 22

Assignment

Answer 22

Giving a value to a variable

Question 23

What is meant by initialising a variable?

Answer 23

Assigning a starting value before the variable data is used or accessed

Question 25

Records in software

Answer 25

A user defined data type which can store a group of data items of different types

Question 25

Integers used to store

Answer 25

Positive or negative whole numbers

Question 26

Strings used to store

Answer 26

one or more text characters

Question 27

Real numbers used to store

Answer 27

Positive and negative whole numbers with decimal places

Question 28

Boolean used to store

Answer 28

A true or false value

Question 29

Why are data types declared before they are used?

Answer 29

Ensures that the required amount of memory is allocated to each variable during the programs execution

Question 31

Data Structure

Answer 31

Used to store multiple items of data together

Question 32

Array

Answer 32

Consists of numbered elements (storage locations)
Each of these stores an item of the same data type
Elements commonly accessed one at a time using repetition (a loop)
An array can be passed as a parameter