DIPT003_Week 9 Arrays

Chapter 7: Arrays

Introduction to Arrays

• Definition: An array is a sequential collection of data storage locations, each capable of holding the same data type.

• Variable Nature: An array is a variable that stores multiple values of the same type.

• Memory Layout: Values are stored in adjacent memory locations.

• Declaration Syntax: Arrays are declared using the [] operator, e.g., int tests[5];.

7.1 Arrays Hold Multiple Values

• Arrays allow the storage of multiple values of a defined data type in a contiguous block of memory.

Array Memory Layout

• When declaring an array such as int tests[5];, memory is allocated for the number of elements specified in the array declaration. The layout is:

  • first element

  • second element

  • third element

  • fourth element

  • fifth element

Array Terminology

• For the declaration int tests[5];:

  • int: The data type of the array elements.

  • tests: The name of the array.

  • 5: The size declarator, indicating the number of elements.

  • Size Calculation: The size of an array is calculated as:
    $ext{size of an array} = ext{(number of elements)} imes ext{(size of each element)}$

Size of Arrays

• Total Memory Size:

  • Example: int tests[5] occupies 20 bytes assuming each int is 4 bytes.

  • Example: long double measures[10] occupies 80 bytes assuming each long double is 8 bytes.

Named Constants as Size Declarators

• Use named constants for better maintainability:

  const int SIZE = 5;
  int tests[SIZE];

• Changes in array size can be easily made by adjusting the constant value.

7.2 Accessing Array Elements

• Each element in an array has a unique subscript starting at 0:

  • Subscripts: 0, 1, 2, 3, 4.

• Last Element Subscript: The last element’s subscript is n - 1, where n is the number of elements.

Using Array Elements

• Array elements can be used just like ordinary variables:

  tests[0] = 79;
  cout << tests[0];
  cin >> tests[1];
  tests[4] = tests[0] + tests[1];

• Attempting to access the entire array using its name is illegal:

  cout << tests; // not legal

Accessing Array Contents

• Elements can be accessed with a literal subscript:

  cout << tests[3] << endl;

• Can also

Introduction to Arrays - Definition: An array is a collection of data storage locations of the same type. - Variable Nature: An array stores multiple values of the same type. - Memory Layout: Values are in adjacent memory locations. - Declaration Syntax: Arrays declared using [], e.g., int tests[5];.

7.1 Arrays Hold Multiple Values - Arrays allow storage of multiple values in contiguous memory.

Array Memory Layout - For int tests[5];, memory is allocated for elements specified. Memory layout consists of: - first element - second element - third element - fourth element - fifth element

Array Terminology - For int tests[5];: - int: Data type. - tests: Array name. - 5: Number of elements. - Size Calculation: $ext{size of an array} = ext{(number of elements)} imes ext{(size of each element)}$

Size of Arrays - Total Memory Size: - Example: int tests[5] occupies 20 bytes (assuming 4 bytes per int). - Example: long double measures[10] occupies 80 bytes (assuming 8 bytes per long double).

Named Constants as Size Declarators - Use named constants for maintainability:

const int SIZE = 5;
int tests[SIZE];

• Adjusting the constant changes array size easily.

7.2 Accessing Array Elements - Each element has a unique subscript starting at 0. - Last Element Subscript: n - 1 (where n is number of elements).

Using Array Elements - Elements can be used like variables:

tests[0] = 79;
cout << tests[0];
cin >> tests[1];
tests[4] = tests[0] + tests[1];

• Accessing the entire array using its name is illegal:

cout << tests; // not legal

Accessing Array Contents - Elements accessed with a subscript:

cout << tests[3] << endl;