Introduction to Computing-Computer Fundamentals-Lecture Slides, Slides of Computer Fundamentals

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Introduction to Computing

Arrays

• Comments
• What are arrays?
• How to declare and initialize arrays?
• Accessing arrays / Using arrays
• One dimensional and Two dimensional arrays
• Arrays and constants

Arrays

• Array
  • Group of consecutive memory locations
  • Same name and type
• To refer to an element, specify
  • Array name
  • Position number
• Format: arrayname [ position number ]
  • First element at position 0
  • n element array named c :
    • c[ 0 ] , c[ 1 ] ... c[ n – 1 ]

Name of array (Note that all elements of this array have the same name, c )

Position number of the element within array c

c[6]

- 6 **0 72 1543

0 62

1 6453 78**

c[0] c[1] c[2] c[3]

c[11]

c[10]

c[9]

c[8]

c[7]

c[5]

c[4]

5

6.3 Declaring Arrays

• When declaring arrays, specify
  • Name
  • Type of array
  • Number of elements arrayType arrayName[ numberOfElements ];
  • Examples: int c[ 10 ]; float myArray[ 3284 ];
• Declaring multiple arrays of same type
  • Format similar to regular variables
  • Example: int b[ 100 ], x[ 27 ];

7

Using Arrays

• Initializers

int n[ 5 ] = { 1, 2, 3, 4, 5 };

• If not enough initializers, rightmost elements become 0 int n[ 5 ] = { 0 }
• All elements 0
• If too many a syntax error is produced syntax error
• C arrays have no bounds checking
• If size omitted, initializers determine it

int n[ ] = { 1, 2, 3, 4, 5 };

• 5 initializers, therefore 5 element array

Accessing Array Components

• The general form (syntax) of accessing an array component is:

arrayName[indexExp]

where indexExp, called index , is any expression whose value

is a nonnegative integer

• Index value specifies the position of the component in the array
• The [] operator is called the array subscripting operator
• The array index always starts at 0

Array Initialization

• As with simple variables
  • Arrays can be initialized while they are being declared
• When initializing arrays while declaring them
  • Not necessary to specify the size of the array
• Size of array is determined by the number of initial values in the

braces

• For example:

double sales[] = {12.25, 32.50, 16.90, 23, 45.68};

Partial Initialization

• The statement

int list[10] = {0};

declares list to be an array of 10 components and initializes all components to zero

• The statement

int list[10] = {8, 5, 12};

declares list to be an array of 10 components, initializes list[0] to 8 , list[1] to 5 , list[2] to 12 and all other components are initialized to 0

Restrictions on Array Processing

Assignment does not work with arrays

In order to copy one array into another array we must copy component-wise

Restrictions on Array Processing

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