Show understanding of the purpose of a record structure to hold a set of data of different data types under one identifier

10.1 Data Types and Records

Objective

Show understanding of the purpose of a record structure to hold a set of data of different data types under one identifier.

What is a Record?

A record (also called a structure in some languages) is a composite data type that groups together a fixed number of elements, called fields, each of which may have a different data type. All the fields are accessed through a single identifier.

Why Use Records?

• Logical grouping of related data (e.g., all information about a student).
• Simplifies passing multiple values to functions or procedures – only one argument is needed.
• Improves code readability and maintainability.
• Provides a clear mapping between real‑world entities and program data.

Typical Syntax (Pseudocode)

record Student
name : string[30]
age  : integer
gpa  : real
enrolDate : date
end record

Example Record: Student

Consider a Student record that stores the following fields:

Memory Layout and Size Calculation

The total size of a record is the sum of the sizes of its fields, plus any padding required for alignment. Assuming no padding, the size is:

\$\text{Size}_{\text{Student}} = 30 + 4 + 8 + 8 = 50\ \text{bytes}\$

If the target architecture aligns fields on 4‑byte boundaries, padding may be added after the name field (30 bytes) to reach the next multiple of 4, giving an extra 2 bytes of padding:

\$\text{Size}_{\text{Student}} = (30 + 2) + 4 + 8 + 8 = 52\ \text{bytes}\$

Accessing Record Fields

Fields are accessed using the dot operator (.) after the record variable name.

student1 : Student
student1.name = "Alice Johnson"
student1.age  = 20
student1.gpa  = 3.75
student1.enrolDate = "2023‑09‑01"

Passing Records to Functions

1. Define a function that takes a record as a parameter.
2. Call the function with a record variable; the whole record is passed as a single argument.

procedure printStudent(s : Student)
output "Name: " + s.name
output "Age: "  + s.age
output "GPA: "  + s.gpa
output "Enrolled: " + s.enrolDate
end procedure
printStudent(student1)

Comparison with Arrays

• Arrays hold multiple values of the same data type, indexed by an integer.
• Records hold a fixed set of values of different data types, each identified by a field name.
• Use an array when you need a homogeneous collection; use a record when you need to model a single entity with heterogeneous attributes.

Key Take‑aways

• A record groups related data of different types under one identifier.
• It simplifies data handling, improves program structure, and mirrors real‑world objects.
• Understanding memory layout helps predict storage requirements and performance implications.