Arrays I
Handling lists of data
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Arrays
A data structure is a group of related
data items.
 The array is one kind of data structure.
 An array is a group of related data
items that all have the same name and
the same data type.
 Arrays are static in that they remain
the same size throughout program
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Arrays
An array is a sequence of data items, all
of the same type that are stored
contiguously in memory.
 Each of the data items is known as an
element of the array
 We can access the individual elements
of the array using an indexing scheme
 Arrays can be of any type we choose.
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Array Declarations

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int array [5] ;
This declaration sets aside a chunk of
memory that’s big enough to hold 5 integers.
It does not initialize those memory locations
to 0 or any other value.
Initializing an array may be done with an
array initializer, as in :
int array [5] = { 5, 2, 6, 9, 3 } ;
array
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5
2
6
9
3
0
1
2
3
4
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Indexing Array Elements
Values of individual elements can be
found by indexing into the array. In our
example, array [0] is equal to 5 and
array [3] is equal to 9.
 The integer in square brackets is called
the subscript.
 The subscript could also be an
expression that evaluates to an integer.
 In our example, array is the name of the
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array.
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Modifying Elements
Individual elements of the array can
also be modified using subscripts.
 array [4] = 20 ; /*changes the value of
the element found at
subscript 4 to 20 */
 Values may be stored in an array using
indexing, rather than using the array
initializer.
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Filling Arrays
Since many arrays are quite large,
using an array initializer is impractical.
 Large arrays are often filled using a for
loop.
for ( i = 0; i < 100; i++)
{
rolls [ i ] = 0 ;
}
would set every element of the 100
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element array, rolls, to 0.
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More Declarations
int score [39] , gradeCounter [5];
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Declares two arrays of type int
Neither array has been initialized
 score contains 39 elements (one for
each student in the class)
 gradeCounter contains 5 elements (one
for each possible grade, A-F)
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Using #define for array sizes
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We often use the
#define to give the
sizes of arrays.
#define SSIZE 39
#define GSIZE 5
main ( )
{
int score [SSIZE] ;
int gradeCounter [GSIZE] ;
}
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