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C - Arrays

Arrays are useful critters that often show up when it would be convenient to have one name for a group of variables of the same type that can be accessed by a numerical index. For example, a tic-tac-toe board can be held in an array and each element of the tic-tac-toe board can easily be accessed by its position (the upper left might be position 0 and the lower right position 8). At heart, arrays are essentially a way to store many values under the same name. You can make an array out of any data-type including structures and classes.

Way to visualize an array is like this:


Let's look at the syntax for declaring an array.

int examplearray[100]; /* This declares an array */

This would make an integer array with 100 slots (the places in which values of an array are stored). To access a specific part element of the array, you merely put the array name and, in brackets, an index number. This corresponds to a specific element of the array. The one trick is that the first index number, and thus the first element, is zero, and the last is the number of elements minus one. The indices for a 100 element array range from 0 to 99. Be careful not to "walk off the end" of the array by trying to access element 100!

char astring[10];
int i = 0;
/* Using scanf isn't really the best way to do this; we'll talk about that 
   in the next tutorial, on strings */
scanf( "%s", astring );
for ( i = 0; i < 10; ++i )
    if ( astring[i] == 'a' )
        printf( "You entered an a!\n" );