Pascal Lesson 8 - Types, Records and Sets

Learn Pascal Programming Tutorial Lesson 8 - Types, Records and Sets

Types

It is possible to create your own variable types using the type statement. The first type you can make is records. Records are 2 or more variables of different types in one. An example of how this could be used is for a student who has a student number and a name. Here is how you create a type:
program Types;

Type
   Student = Record
      Number: Integer;
      Name: String;
   end;

begin
end.
After you have created the type you must declare a variable of that type to be able to use it.
program Types;

Type
   StudentRecord = Record
      Number: Integer;
      Name: String;
   end;

var
   Student: StudentRecord;

begin
end.
To access the Number and Name parts of the record you must do the following:
program Types;

Type
   StudentRecord = Record
      Number: Integer;
      Name: String;
   end;

var
   Student: StudentRecord;

begin
   Student.Number := 12345;
   Student.Name := 'John Smith';
end.
The other type is a set. Sets are not very useful and anything you can do with a set can be done just as easily in another way. The following is an example of a set called Animal which has dog, cat and rabbit as the data it can store:
program Types;

Type
   Animal = set of (dog, cat, rabbit);

var
   MyPet: Animal;

begin
   MyPet := dog;
end.
You can't use Readln or Writeln on sets so the above way of using it is not very useful. You can create a range of values as a set such as 'a' to 'z'. This type of set can be used to test if a value is in that range.
program Types;

uses
   crt;

Type
   Alpha = 'a'..'z';

var
   Letter: set of Alpha;
   c: Char;

begin
   c := ReadKey;
   if c in [Letter] then
      Writeln('You entered a letter');
end.

• Learn Pascal Programming Tutorial Lesson 1 - Introduction to Pascal
• Learn Pascal Programming Tutorial Lesson 2 - Colors, Coordinates, Windows and Sound
• Learn Pascal Programming Tutorial Lesson 3 - Variables and Constants
• Learn Pascal Programming Tutorial Lesson 4 - String Handling and Conversions
• Learn Pascal Programming Tutorial Lesson 5 - Decisions
• Learn Pascal Programming Tutorial Lesson 6 - Loops
• Learn Pascal Programming Tutorial Lesson 7 - Arrays
• Learn Pascal Programming Tutorial Lesson 8 - Types, Records and Sets
• Learn Pascal Programming Tutorial Lesson 9 - Procedures and Functions
• Learn Pascal Programming Tutorial Lesson 10 - Text Files
• Learn Pascal Programming Tutorial Lesson 11 - Data Files
• Learn Pascal Programming Tutorial Lesson 12 - Units
• Learn Pascal Programming Tutorial Lesson 13 - Pointers
• Learn Pascal Programming Tutorial Lesson 14 - Linked Lists