1. Multiple-Subscripted Array
What it is
How to use it
How to declare it
How to initialize it

2. Multiple-Subscripted Arrays
Use more than one subscript (can have up to 12)
Double-subscripted array (2 subscripts)

3. Double-subscripted array
good for representing tables in memory
one subscript is the row
second subscript is the column

4. Double-subscripted array
column 0
column 1
column 2
column 3
row 0
a[0][0]
a[0][1]
a[0][2]
a[0][3]
row 1
a[1][0]
a[1][1]
a[1][2]
a[1][3]
a[2][0]
a[2][1]
a[2][2]
a[2][3]
row 2
column subscript
row subscript
array name = a
a double-subscripted array with 3 rows and 4 columns
3 by 4 array

5. Referencing elements in a double-subscripted array
To set the element in row 2 and column 3 to the value 4 use:
a [2] [3] = 4;
column subscript
row subscript
name of the array

6. Declaring a 3 by 4 array int a [3] [4];
must tell compiler name, size (2 sizes) and type
all elements of the array must be the same type
any data type is fine (int, float, char, etc.)

7. Declaring a double-subscripted array
Must use constants to declare row and column sizes.
int a [3] [4];
char letters [2] [26];
#define ROW 3
#define COLUMN 4
int a [ROW] [COLUMN];
const int row = 3;
const int column = 4;
int a [row] column];
const int array_size 5 defines array_size to be a constant variable that cannot be changed. It will always hold the number 5. constant variables may be used to declare the size of an array since they don’t change.

8. Initializing a double-subscripted array
const int row = 3;
const int column = 4;
int a [row] [column];
for (int i = 0; i < row; i++) {
for (int j = 0; j < column; j++) {
a [i][j] = 0; }

9. Initializing a double-subscripted array with declaration
const int row = 3;
const int column = 4;
int a[row] [column] = {{1,2,3,4},
{1,2,3,4},
{1,2,3,4}}; 1 2 3 4 3 1 2 4 3 4 1 2

10. Initializing a double-subscripted array with declaration
const int row = 3;
const int column = 4;
int a[row] [column] = {{1,2,3},
{1,2},
{1,2,3,4}}; 1 2 3 1 2 3 4 1 2

11. Setting entire array to 0
const int row = 3;
const int column = 4;
int a [row] [column] = {0};

12. Exercises
Answer the following questions regarding an array called table that is a double-subscripted array with 2 rows and 3 columns.
1) Define constant variables numRows and numCols to be used to declare the array.
2) Declare the array to be an integer array.
3) Use a for loop to initialize each element of the array to be the sum of it’s subscripts
4) Write a code segment to print the array as a table.

13. How double-subscripted arrays are stored in memory
table 1 2 3 4 5 6 7 8 9 10 11 12
table 1 2 3 4 5 6 7 8 9 10 11 12

14. passing double-subscripted array to a function
Must tell function size of second subscript so it can find the beginning of each row in memory.
void PrintTable (int table [ ] [4], int numRows, int numCols) {
for (int i = 0; i < numRows; i++) {
for (int j = 0; j < numCols; j++) {
cout << setw(4) << table [i] [j]; }
cout << endl;

15. passing double-subscripted array to a function
passed as reference parameter
Use const to prevent function changing the array.
void PrintTable (const int table [ ] [4], int numRows, int numCols);

16. Exercises Write a main program as follows:
Use the results of the last set of exercises to declare an array of type integers with 2 rows and 3 columns and initialize each element to the sum of it’s subscripts. Call the PrintTable function to print the array.
Create a function called PrintTable to print each element of the array in tabular form.