Overview

CHAPTERS 13 AND 14 DESCRIBED OPENVMS FILES and presented methods for manipulating files as a whole. This chapter begins the presentation of DCL commands that operate on the contents of files: commands for reading, writing, and updating files. In particular, this chapter addresses sequential files, which are collections of data that can only be accessed in order from beginning to end. Chapter 17 addresses indexed files.

When a program performs file operations such as reading and writing, the operations are carried out by the OpenVMS Record Management System, or RMS. This chapter and later chapters will refer to RMS when discussing file operations.

A sequential file is a file made up of a sequence of individual records. Each record contains some logically related information, while all the records taken together contain the sum total of information in the file. One of the distinguishing features of sequential files is that the records are arranged in a particular sequence and can only be accessed in that order. The file is written one record at a time, from beginning to end, and afterwards can only be read in the same order.

The records in a sequential file can be composed of free-format text, or they can be laid out in a predefined format called a record structure. This chapter assumes that sequential files contain free-format text; record structures are described in the next two chapters. In a sequential, free-format text file, or simply text file, each record...