# D3 overview

D3 is a generalized database management language and system that
provides tools to manage information in a flexible, efficient, and
timely manner. The essence of developing an application with D3 is
to define the problem in terms of information and relationships
between information.

D3 is a multiuser system that supports many terminals and runs
many jobs simultaneously. Processing originates with commands
entered using Terminal Control Language (TCL) and ACCESS
statements, which are a combination of commands and parameters
contained in files called master dictionaries. Each set of
interrelated files or database in D3 is organized around an master
dictionary. The master dictionary contains the commands (both
provided with the system and cataloged programs that are part of an
application), macros, menus, connectives, and file names needed to
process the information in its database.

This document contains entries specific to D3 features and is
divided into major sections (see below). Each entry contains a
description, syntax, options, and examples as appropriate.

Note:
References to commands can appear in more than one section.

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Source: https://d3codex.com/introduction/d3-overview/ - part of the D3Codex reference.