Computer Science 9618/33 — May/June 2022

Background Concept

A record is a composite data type made up of several named fields. Each field stores one value, and each field has its own data type. In the given definition, LibraryRecord has four fields:

• Title : STRING
• Fiction : BOOLEAN
• Author : STRING
• NumberOfCopies : INTEGER

When a variable is declared as that record type, each field is accessed using dot notation:

RecordVariable.FieldName

So if LibraryBook is a LibraryRecord, then LibraryBook.Title means the Title field inside that specific record.

Understanding the Question

The question gives the record type and then says that LibraryBook has already been declared as one variable of that type:

DECLARE LibraryBook : LibraryRecord

You are asked to write pseudocode statements that assign:

• the string A Level Computer Science to the Title field
• the Boolean value FALSE to the Fiction field

So this is not asking you to redefine the type or redeclare the variable. It is only asking for assignment statements to two fields inside the record.

Approach

Use one assignment statement per field. For each one:

1. Write the record variable name: LibraryBook
2. Add a dot and the field name
3. Use the assignment arrow ←
4. Put the correct value on the right-hand side

Because Title is a STRING, the text must be in double quotes. Because Fiction is a BOOLEAN, use the keyword FALSE without quotes.

Step-by-Step Reasoning

The first field is Title.

• The variable is LibraryBook
• The field is Title
• The value to store is the text A Level Computer Science

So the statement is:

LibraryBook.Title ← "A Level Computer Science"

The second field is Fiction.

• The variable is still LibraryBook
• The field is Fiction
• The value to store is the Boolean value FALSE

So the statement is:

LibraryBook.Fiction ← FALSE

These are the only two lines needed.

Key Takeaways

• A record field is accessed with dot notation.
• Assign values to record fields using the assignment arrow ←.
• Strings need quotes; Boolean values such as TRUE and FALSE do not.

Common Mistakes

• Writing LibraryRecord.Title instead of LibraryBook.Title. LibraryRecord is the type name; LibraryBook is the variable.
• Using = instead of ← in pseudocode.
• Writing "FALSE" in quotes. That would make it a string, not a Boolean.
• Omitting the field name and trying to assign directly to LibraryBook.

Things to Be Careful About

• Use the exact field names given: Title and Fiction.
• Keep the identifier casing exactly as shown in the question.
• In Cambridge pseudocode, assignment uses ←, not =.
• Only write the assignment statements asked for; do not repeat the type definition or declaration.

Background Concept

Data types describe what kind of values can be stored and how those values are organised. Some data types are built in, such as INTEGER, REAL, STRING, CHAR and BOOLEAN. Others are created by the programmer to match the problem being solved.

A user-defined data type is one designed by the programmer. This is useful when built-in types alone do not represent the structure of the data clearly.

A composite data type is one that contains multiple components. Those components may all be the same type, or they may be different types. A record is a common composite type because it groups several related fields together under one name.

Understanding the Question

The question states that a record is a user-defined composite data type and then asks you to explain what that means. So there are really two ideas to explain:

1. what "user-defined" means
2. what "composite" means

It also asks for another example. That means you should not stop after a definition; you should include a valid example of a programmer-created type made from multiple fields.

Approach

A full-mark answer should contain three parts:

• say that the type is created by the programmer
• say that it consists of several related items/fields
• give an example of another such type

A short record definition is the clearest example because it directly shows multiple named fields.

Step-by-Step Reasoning

First, explain "user-defined".

This means the programmer defines the type themselves. It is not one of the standard built-in types already provided by the language.

Second, explain "composite".

Composite means the type is made from more than one component. In a record, these components are fields. Each field stores related information, and the fields can have different data types.

For example, a student record might need a name, candidate number and date of birth. These are related items about one student, so grouping them into one type makes sense.

That leads to a suitable example:

TYPE StudentRecord
  DECLARE Name : STRING
  DECLARE CandidateNumber : INTEGER
  DECLARE DateOfBirth : STRING
ENDTYPE

This example is:

• user-defined, because the programmer created StudentRecord
• composite, because it contains several fields

Key Takeaways

• "User-defined" means created by the programmer for a specific problem.
• "Composite" means made up of multiple data items or fields.
• Records are a standard way to build a user-defined composite type.
• Good examples show both the type name and its component fields.

Common Mistakes

• Defining only "record" without explaining "user-defined" and "composite" separately.
• Saying only that it stores "lots of data" without stating that it contains multiple fields.
• Giving a built-in type like INTEGER as the example. That is not user-defined.
• Giving a one-field example, which does not clearly show a composite type.

Things to Be Careful About

• The question asks for another example, so do not just repeat LibraryRecord without adding anything new.
• Make it clear that the fields are related and grouped into one structure.
• If you give an example in pseudocode, keep the format correct with TYPE ... ENDTYPE and DECLARE lines.
• A concise explanation is enough, but it must include both parts of the term and an example.