Why do Objective-C files use the .m extension?

Since I started learning Objective-C and Cocoa, I've been wondering why they have chosen the extension .m for the implementation files - was it supposed to mean something, or was it just a random letter?

.m files contain the (m)ethods. Possible reason?

Today most people would refer to them as "method files", but

> "The .m extension originally stood for
> "**m**essages" when Objective-C was first
> introduced, referring to a central
> feature of Objective-C [...]"

(from the book "[Learn Objective-C on the Mac][1]" by Mark Dalrymple and Scott Knaster, page 9)

**EDIT:** To satisfy an itch I emailed [Brad Cox][2], the inventor of Objective-C, about the question and he answered with this single line:

> "Because .o and .c were taken. Simple
> as that."

Here's the email as visual proof:

![Visual Proof][3]



[1]:

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[2]:

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[3]:

It stands for "methods". From the [comp.lang.objective-C FAQ][1]:

> The organisation of Objective-C source is typically similar to that of C or C++ source code, with declarations and object interfaces going into *header* files named with a .h extension, and definitions and object implementations going in files named with a .m (short for *methods*) extension.

[1]:

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