Many LaTeX classes (including the standard book class) number things per chapter; so figures in chapter 1 are numbered 1.1, 1.2, and so on. Sometimes this is not appropriate for the user's needs.
Short of rewriting the whole class, one may use one of the
removefr and remreset packages; both define a
\@removefromreset command, and having included the package one
writes something like:
\makeatletter
\@removefromreset{figure}{chapter}
and the automatic renumbering stops. You then need to redefine the
way in which the figure number (in this case) is printed:
\renewcommand{\thefigure}{\@arabic\c@figure}
\makeatother
(remember to do the whole job, for every counter you want to
manipulate, within \makeatletter ... \makeatother).
The technique may also be used to change where in a multilevel structure a counter is reset. Suppose your class numbers figures as <chapter>.<section>.<figure>, and you want figures numbered per chapter, try:
\@removefromreset{figure}{section}
\@addtoreset{figure}{chapter}
\renewcommand{\thefigure}{\thechapter.\@arabic\c@figure}
(the command \@addtoreset is a part of LaTeX itself).
The chngcntr package provides a simple means to access the
two sorts of changes discussed, defining \counterwithin and
\counterwithout commands.
\input{removefr})