An int variable is used to store an integer (whole number) value. An integer value is one of 0, ~+mn~1, ~+mn~2, ~+mn~3, ~+mn~4, etc. However, on a computer, the largest and smallest integers which can be stored are determined by the number of bits used to store an integer.
Typically, an int variable occupies 16 bits (2 bytes) and can be used to store whole numbers in the range -32,768 to +32,767. Note, however, that on some machines, an int could occupy 32 bits, in which case it can store whole numbers from -2,147,483,648 to +2,147,483,647. In general, if n bits are used to store an int, the range of numbers which can be stored is -2(n-1) to +2(n-1) - 1.
Integer constants can be written in various ways. The most common form is the one we are all accustomed to, using decimal digits, for example, 354, -1, 32905 and 987654321. Note that you are allowed to use only a possible sign (+ or -) followed by digits 0 to 9. In particular, you cannot use commas as you might do to separate thousands; thus 1,713 is an invalid integer constant—you must write it as 1713.