OutputStream is an abstract class from which all byte-oriented output streams are derived. Its descendant classes are used for general-purpose (non-character output). These streams are aimed at writing groups of 8-bit bytes to output destinations. The bytes are in the same format as Java primitive types. For example, 4-byte groups corresponding to type int can be written to a disk file.

We will mostly be interested in FileOutputStream and DataOutputStream. We have used PrintStream many times already, because System.out is an object of that type.