Machine instructions operate on data. Data can be categorised as follows :
Addresses: It basically indicates the address of a memory location. Addresses are nothing but the unsigned integer, but treated in a special way to indicate the address of a memory location. Address arithmatic is somewhat different from normal arithmatic and it is related to machine architecture.
Numbers: All machine languages include numeric data types. Numeric data are classified into two broad categories: integer or fixed point and floating point.
Characters: A common form of data is text or character strings. Since computer works with bits, so characters are represented by a sequence of bits. The most commonly used coding scheme is ASCII (American Standard Code for Information Interchange) code.
Logical Data: Normally each word or other addressable unit (byte, halfword, and so on) is treated as a single unit of data. It is sometime useful to consider an n-bit unit as consisting of n 1-bit items of data, each item having the value 0 or 1. When data are viewed this way, they are considered to be logical data. Generally 1 is treated as true and 0 is treated as false.