Arrays

1
Arrays
Foundation Studies Course
2
Introduction

• An array is a structure which holds many
  variables, all of the same data type.
• The array consists of so many elements, each
  element of the array capable of storing one piece
  of data (ie, a variable).

3
Definition

• An array is defined as follows
• array_name ARRAY lower..upper of data_type
• Lower and Upper define the boundaries for the
  array.
• Data_type is the type of variable which the array
  will store, eg, type int, char etc.

4
Declaring Arrays

• A typical declaration follows
• VAR
• marks ARRAY 1..20 of integer
• This creates a definition for an array of
  integers called marks, which has 20 separate
  locations numbered from 1 to 20. Each of these
  positions (called an element), holds a single
  integer.

5
Assigning Values

• To assign a value to an element of an array, use
• marks2 10
• This assigns the integer value 10 to element 2 of
  the marks array. The value or element number
  (actually its called an index) is placed inside
  the square brackets.
• To assign the value stored in an element of an
  array to a variable, use
• Var
• totalinteger
• total marks1marks2 marks10
• This takes the integer stored in element 1 to 10
  of the array marks, and makes the integer total
  equal to it.

6
Example

• program Simple
• var name string
• maths,english,maltese,total integer
• average real
• begin
• Write('Enter name of student ')
• readln(names)
• write('Enter marks for Maths --gt ')
• readln(maths)
• write('Enter marks for English --gt
  ')
• readln(english)
• write('Enter marks for Maltese --gt
  ')
• readln(maltese)

7
Example

• program Simple_Arrays
• var index integer
• names array 1..10 of string
• maths,english,maltese,total array 1..10 of
  integer
• average array 1..10 of real
• begin
• for index 1 to 10 do
• begin
• Write('Enter name of student
  ',Index,' ')
• readln(namesindex)
• write('Enter marks for Maths --gt ')
• readln(mathsindex)
• write('Enter marks for English --gt
  ')
• readln(englishindex)

8
Lab

• In order to store the telephone numbers of his
  friends, a programmer decided to make use of two
  1-dimensional arrays to store the names and the
  corresponding phone numbers.
• Garfield Asterix Taz
• 79312444 99453552 79266262
• Write a short program to enter and store up to
  fifty names and telephone numbers. Ensure that
  the exact variable declarations are made as well
  as the correct program syntax in general is
  used.