In 1837, Charles Babbage (a British mathematician) first described the Analytical Engine, which historians since have called the first workable design for a punch card computer. The Engine was never built, however, because Babbage himself was a jerk to work with and alienated a lot of his supporters (by all accounts), not to mention the political, financial and legal issues that surrounded the project.
The Analytical Engine is interesting because it predated the first electro-mechanical computers (the German Zuse Z3 and the American Atanasoff–Berry Computer) by more than 100 years. In many ways, it might have been more powerful than those first computers developed in the 1940s, except Babbage's design was more or less forgotten about in the world of mathematics and computer science. In "The Difference Engine," William Gibson and Bruce Sterling show their views on how Victorian England would've changed if Babbage had actually built the Engine. It's a very interesting read anyway, being one of the founding works of steampunk and all, outside its stance as a thought experiment.
Babbage's machine ran off the same style of punch cards Joseph Jacquard developed to run his looms, which were pieces of punched metal strung together into one long sheet. These were not the card-stock version Herman Hollerith developed in the 1880s for the U.S. Census, but did manage to create enough of a precedence for Hollerith to not get a patent.
What's this all mean for the writer of steampunk? Well that depends on how technology heavy you want to get in your story. If you don't want to deal with computers and punch cards (I do because I'm weird, but you already knew that) then you can safely ignore this aspect of Victorian technology. If, however, you want to include things like automatons and computer-controlled equipment, then you must of necessity make them run on punch card programming.
I could go into detail about punch cards, but that would probably make your eyes glaze over* (it's all very technical and not really necessary unless you're writing a character who has to explain it at some point). Suffice it to say, if you want computer functionality in a steampunk world, then mechanical computers are the way to go. And as with everything steampunk, the design of your mechanical computer is up to you. Happy writing, fellow travelers.
*If you really want a detailed discussion on punch-card programming, feel free to email me.