which directory contains the .cshrc file on a macpro using el captain

According to the man page for csh, it is in the user's home directory.

I would imagine you have to be using the c shell for it to exist (or even need to).

There is no requirement for it to exist unless you need it, then it would be up to you to create.

Also according to the man page, it will defer to .tcshrc if it exists.

So, since the c shell is not used by OS X and you would need to create the file yourself, the answer to you question is that no directory contains that file unless you created it.

See "man csh"

Startup and shutdown

A login shell begins by executing commands from the system files /etc/csh.cshrc and

/etc/csh.login. It then executes commands from files in the user's home directory:

first ~/.tcshrc ➕ or, if ~/.tcshrc is not found, ~/.cshrc, then ~/.history (or

the value of the histfile shell variable), then ~/.login, and finally ~/.cshdirs

(or the value of the dirsfile shell variable) (+). The shell may read

/etc/csh.login before instead of after /etc/csh.cshrc, and ~/.login before instead

of after ~/.tcshrc or ~/.cshrc and ~/.history, if so compiled; see the version

shell variable. ➕

Non-login shells read only /etc/csh.cshrc and ~/.tcshrc or ~/.cshrc on startup.

For examples of startup files, please consult http://tcshrc.sourceforge.net.

Commands like stty(1) and tset(1), which need be run only once per login, usually

go in one's ~/.login file. Users who need to use the same set of files with both

csh(1) and tcsh can have only a ~/.cshrc which checks for the existence of the tcsh

shell variable (q.v.) before using tcsh-specific commands, or can have both a

~/.cshrc and a ~/.tcshrc which sources (see the builtin command) ~/.cshrc. The

rest of this manual uses `~/.tcshrc' to mean `~/.tcshrc or, if ~/.tcshrc is not

found, ~/.cshrc'.

In the normal case, the shell begins reading commands from the terminal, prompting

with `> '. (Processing of arguments and the use of the shell to process files con-

taining command scripts are described later.) The shell repeatedly reads a line of

command input, breaks it into words, places it on the command history list, parses

it and executes each command in the line.

One can log out by typing `^D' on an empty line, `logout' or `login' or via the

shell's autologout mechanism (see the autologout shell variable). When a login

shell terminates it sets the logout shell variable to `normal' or `automatic' as

appropriate, then executes commands from the files /etc/csh.logout and ~/.logout.

The shell may drop DTR on logout if so compiled; see the version shell variable.

The names of the system login and logout files vary from system to system for com-

patibility with different csh(1) variants; see FILES.

And ~ is the C-Shell short-cut for your home directory.

Is it not in private>etc?