Data Structures [1]

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Data Structures 1
CP1
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Arrays

• All data must be the same data type.
• Eg. (Daily sales figures for John - to nearest )
• Mon 240
• Tue 230
• Wed 180
• Thu 270
• Fri 120
• (All of data type Integer)

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In Visual Basic

• Dim Sales(5) As Integer
• A one-dimensional array has one subscript to
  identify the element of the array.
• Eg.
• Mon 240
• Tue 230
• Wed 180
• Thu 270
• Fri 120

?Sales(4)
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Two-dimensional Arrays

• Data must be the same type.
• A two-dimensional array has 2 subscripts.

Eg. Sales figures for John, Mary and
Sue John Mary Sue Mon 240 420 140 Tue 230 380 1
90 Wed 180 400 210 Thu 270 360 240 Fri 120 320 190
? Sales(4,2)
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Three-dimensional Arrays

• Data must be the same type.
• A two-dimensional array has 3 subscripts.

Eg. Sales figures for John, Mary and Sue for each
of three different items
Item 1 John Mary Sue Mon 240 420 140 Tue 230 380 1
90 Wed 180 400 210 Thu 270 360 240 Fri 120 320 190

Item 2 John Mary Sue Mon 440 440 120 Tue 530 380 3
90 Wed 480 440 280 Thu 670 365 540 Fri 150 310 490

Item 3 John Mary Sue Mon 210 430 120 Tue 130 280 1
90 Wed 120 100 220 Thu 270 320 143 Fri 120 220 295

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• and YES! In programming you can have Arrays with
  more than three dimensions
• All data must be of the same data type
• An n-dimensional array would use n subscripts to
  identify each element.

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Records

• Data may be of different types
• Eg. (Name, Form, DOB, Exam mark)
• John Smith
• 12 T
• 12/04/85
• 65

(Text strings, a date and a number)
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In Visual Basic

• Structure PupilType
• Dim PupilName As String
• Dim Form As String
• Dim DOB As Date
• Dim ExamMark As Integer
• End Structure

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• Structure PupilType
• Dim PupilName As String
• Dim Form As String
• Dim DOB As Date
• Dim ExamMark As Integer
• End Structure
• A variable Pupil can be declared as being of type
  PupilType, and the fields assigned
• Dim Pupil As PupilType
• Pupil.PupilName John Smith
• Pupil.Form 12T
• Pupil.DOB12.04.85
• Pupil.ExamMark 65

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Arrays of Records
An array of records is sometimes called a
TABLE. Each record has a subscriptIf this table
was called Markbook, then Markbook(4).ExamMark
is 44.
PupilName Form DOB ExamMark
1 John Smith 12T 12/04/85 65
2 Sally Jones 12G 15/05/85 78
3 Tom Jenkins 12G 19/11/84 52
4 Ruby Day 12T 06/01/85 44
5 Jenny Thomas 12B 07/12/84 60