documentclass

Documentclass is a core LaTeX command used to specify the overall class and formatting rules for a document. The command has the form \documentclass[options]{class} and must appear as the first non-comment line in a LaTeX source file, before \begin{document}. The class file (.cls) defines the document’s structure, default typography, available sectioning commands, and other formatting conventions for that class.

Commonly used classes include article, report, book, and letter, with beamer used for presentations. Each class provides its own default behaviors and may impose specific requirements or capabilities, such as chapter handling in book or title page behavior in certain classes. The chosen class influences not only the appearance but also how packages interact with the document.

Options passed to documentclass control broad aspects of layout and typography. Typical options include font size (10pt, 11pt, 12pt), paper size (a4paper, letterpaper, etc.), and layout choices (oneside, twoside; onecolumn, twocolumn). Other options may affect draft mode, final rendering, or be specific to a class (for example, how titles or abstracts are handled).

In practice, authors select a class at the start of the document, then load additional packages in the preamble to extend functionality, and place the content within \begin{document} … \end{document}. The document class thus establishes the foundational format, with packages and customizations providing further refinements.