Arrays

INTRODUCTION
• Array a collection of a fixed number of
components wherein all of the components
have the same data type
• In a one-dimensional array, the
components are arranged in a list form
• Syntax for declaring a one-dimensional
array:

Defining Arrays
• When defining arrays, specify
–Name
–Type of array
–Number of elements
• arrayType arrayName[ numberOfElements ];
–Examples:
• int c[ 10 ];
• float myArray[ 3284 ];

Accessing Array Components
• General syntax:
where indexExp, called an index, is any expression whose value
is a nonnegative integer
• Index value specifies the position of the component
in the array
• [ ] is the array subscripting operator
• The array index always starts at 0

One-Dimensional Arrays
• Some basic operations performed on a one-
dimensional array are:
– Initializing
– Inputting data
– Outputting data stored in an array
– Finding the largest and/or smallest element
• Each operation requires ability to step through
the elements of the array
• Easily accomplished by a loop

Processing One-Dimensional Arrays
• Consider the declaration
int list[100]; //array of size 100
int i;
• Using forloops to access array elements:
for (i = 0; i < 100; i++) //Line 1
//process list[i] //Line 2
• Example:
for (i = 0; i < 100; i++) //Line 1
cin >> list[i]; //Line 2

Array Initialization During
Declaration
• Arrays can be initialized during
declaration.
 In this case, it is not necessary to specify the size of
the array
 Size determined by the number of initial values in
the braces
• Example:
double sales[] = {12.25, 32.50, 16.90, 23,
45.68};

Array Index Out of Bounds
• If we have the statements:
double num[10];
int i;
• The component num[i] is valid if i = 0, 1, 2,
3, 4, 5, 6, 7, 8, or 9
• The index of an array is in bounds if the
index >=0 and the index <=ARRAY_SIZE-1
• Otherwise, we say the index is out of
bounds
• In C++, there is no guard against indices
that are out of bounds

Two- and Multidimensional
Arrays
• Two-dimensional array collection of a fixed
number of components (of the same type)
arranged in two dimensions
– Sometimes called matrices or tables
• Declaration syntax:
where intexp1 and intexp2 are expressions
yielding positive integer values, and specify the
number of rows and the number of columns,
respectively, in the array

Two- and Multidimensional Arrays

Accessing Array Components
• Syntax:
where indexexp1 and indexexp2 are
expressions yielding nonnegative integer
values, and specify the row and column
position

Two-Dimensional Array Initialization
During Declaration
• Two-dimensional arrays can be initialized
when they are declared:
• Elements of each row are enclosed within
braces and separated by commas
• All rows are enclosed within braces
• For number arrays, if all components of a row
aren’t specified, unspecified ones are set to 0

Processing Two-Dimensional Arrays
• Ways to process a two-dimensional array:
– Process the entire array
– Process a particular row of the array, called
row processing
– Process a particular column of the array,
called column processing
• Each row and each column of a two-
dimensional array is a one-dimensional
array
– To process, use algorithms similar to
processing one-dimensional arrays

Processing Two-Dimensional Arrays

MultidimensionalArrays
• Multidimensional array collection of a fixed
number of elements (called components)
arranged in n dimensions (n >= 1)
• Also called an n-dimensionalarray
• Declaration syntax:
• Toaccess a component:

MultidimensionalArrays (cont'd.)
• When declaring a multidimensional array
as a formal parameter in a function
 Can omit size of first dimension but not other
dimensions
• As parameters, multidimensional arrays
are passed by reference only
• A function cannot return a value of the
type array
• There is no check if the array indices
are within bounds

Arrays

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Arrays