C Pocket Reference

Arrays

Arrays are used to manage large numbers of objects of the same type. Arrays in C can have elements of any type except a function type. The definition of an array specifies the array name, the type, and, optionally, the number of array elements. For example:

    char line[81];

The array line consists of 81 elements with the type char. The variable line itself has the derived type “array of char" (or "char array”).

In a statically defined array, the number of array elements (i. e., the length of the array) must be a constant expression. In ANSI C99, any integer expression with a positive value can be used to specify the length of a non-static array with block scope. This is also referred to as a variable-length array .

An array always occupies a continuous location in memory. The size of an array is thus the number of elements times the size of the element type:

sizeof( line ) == 81 * sizeof( char ) == 81 bytes

The individual array elements can be accessed using an index. In C, the first element of an array has the index 0. Thus the 81 elements of the array line are line[0], line[1], ... , line[80].

Any integer expression can be used as an index. It is up to the programmer to ensure that the value of the index lies within the valid range for the given array.

A string is a sequence of consecutive elements of type char that ends with the null character, '\0'. The length of the string is the number of characters excluding the string terminator '\0'. A string is stored in a char array, ...