Arrays

• Apart from the broad spectrum of data types, C++ supports arrays. This data type is useful when a group of elements are to be represented by a common name.
• An array is a group of elements that share a common name, that are differentiated from one another by their positions within the array. An array is a collection of homogeneous data.
• For example, 21, 20, 14, 25 and 13 are marks in 5 subjects of a student. To store these five marks, five variables would be required test1, test2, test3, test4 and test5. For such a representation, arrays are useful. This can be represented as test The ability of using a single name to represent a collection of items and to refer to an item by specifying the location number enables the programmer to develop concise and efficient programs

  Declaring arrays

• An array must be declared, since it is basically a variable.
• Syntax: type variable-name [size]; Example: int marks[5];
• This example describes an array of 5 integer elements and the elements are numbered starting with 0. Each element is accessed by the array name followed by its position in square brackets. This position is known as the subscript, thus each array statement is a subscripted variable. Therefore, you would have: mark mark[0], mark[1], mark[2], mark[3] and mark[4].
• If the array is accessed beyond its limit, C++ does not report it as an error. Having declared mark, accessing mark[5] is not a syntax error. The program does not terminate abnormally, though it is a logical error as the last legal element is mark[4]
• One Dimensional Array is a list of data items that can be given one variable name using one subscript and such a variable is called a one dimensional array.
• The array storage starts from 0 and hence the loop termination is i < 10. The second loop is to display the 10 integers.

  Initialization of Arrays

• An array can be initialized along with its declaration.
• SYNTAX: static type array-name[size]={val1,val2...};
• static int count[3]={0,0,0};
• will declare the variable count as an array of size 3 and will assign zero to each element. Note that this declares a static variable. The size parameter may be omitted. In such cases, the compiler allocates enough spaces for all initialized elements.
• static int count[]={0,0,0};

  Two Dimensional Arrays

• The following table could be considered as a two dimensional array:
• Then score[0][0] represents the marks of the first student and score[0][1] the rank of the first student.
• C++ allows us to define such a table of items by defining a two dimensional array.
• As with the single dimensional array, each element of the array is indexed from zero to its maximum size minus one, the first index stands for row and the second index for column. C++ uses the row major arrangement to access the elements of the array - first number represents the row and the second number represents the column.

  Declaration

• int score [3][2]
• will declare a table of 3 rows and 2 columns.
• Initialization: Similar to the one dimensional arrays, two dimensional arrays can also be initialized.
• static int table[2][3]={0,0,0,1,1,1};
• initializes the elements of the first row to zero and the second row to one. Note that initialization is done row by row. For better degree of readability, you can also write the same initialization in the matrix form, as:
• static int table[2][3]={{0,0,0},{1 ,1 ,1}};
• The inner braces are optional, but it is good practice to use them, as they improve the readability.

  # include < iostream.h > 
  void main()
  int num[3][3];
  int i,j;
  cout << “Enter the numbers into the array” << endl; 
  for (i=0;i < 3;i++)
  {
  for (j=0;j < 3;j++)
  cin >> num[i][j];
  }
  for (i=0;i<3;i++)
  {
  for (j=0;j<3;j++)
  cout << num[i][j] << ‘\t’;
  cout << endl;
  }
  }
  Multidimensional Arrays C++ permits arrays of more than two dimensions. The maximum number of dimensions depends on the compiler.
  SYNTAX: type array-name[s1][s2][s3]...[sm];
  Click here for example
  

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