Very first season, it's why they leave the girl (played by Mackenzie Davis, and I can't remember the character's name) alone in a closet with a computer terminal and a big binder, the binder had been written by the other two main protagonists beforehand.

This is the main plot point in S01E01, when Gordon Clark and Joe MacMillan reverse engineer the IBM and dump the BIOS (and is later mentioned a few times when Cameron Howe is rewriting the BIOS).

Spoilers ahead if you haven't watched the show (quotes from S01E01: I/O):

> Gordon Clark: A personal computer, like any other computer, is just a nothing box full of electronic switches and hardware. You know, the IBM, the Altair, the Apple II... it's all the same junk. Anyone can buy all this stuff off the shelf right now. It's called "open architecture." I mean, IBM, they basically don't own anything inside the machine.

> Joe MacMillan: Except the chip.

> Gordon Clark: Yeah, well, except what's on the chip. The BIOS is on one of these chips, we just don't know which one. The ROM BIOS is the only part of the machine IBM actually designed. I mean, it is the program, it is the magic. The bad news is they copyrighted it and they own how it works. The good news is there's a way around that, sort of.

> Joe MacMillan: Reverse engineering.

After dumping the BIOS, IBM decides to sue Cardiff Electric because Joe MacMillan tells IBM about their little "side project", forcing the company to dedicate resources towards actually building a IBM PC clone. In the meeting with Cardiff Electric's lawyer (Barry Shields), they agree to do a clean room implementation.

> John Bosworth: Why can't we fire these peckerheads?

> Barry Shields: Because then you'll lose this lawsuit. Fire them, shelve their work, you're essentially admitting guilt.

> John Bosworth: Okay, so what's the solution, Barry?

> Barry Shields: We legitimize the project.

> John Bosworth: What?

> Barry Shields: Go the other way. We say Cardiff Electric as a company has been pursuing PC development all along. You take Clark's findings on the BIOS chip, you tell an engineer to build a unit that operates and performs in exactly the same way, but you don't tell him how to do it.

> John Bosworth: Hell, I don't think we have one engineer capable of building a BIOS from scratch other than "Sonny Bono" over here.

> Barry Shields: And you can't use him or any other engineer we currently employ.

> John Bosworth: So we have to hire?

> Barry Shields: Yes, someone who doesn't know us or IBM, and certainly hasn't seen the contents of this binder. Essentially, all the law stipulates is that he can't be hands-on in the actual chip creation.

> John Bosworth: And we can't fire them.

> Barry Shields: No, not right now.

> John Bosworth: So we get out of this by actually building a PC clone? This is your brilliant idea to save our hides, Barry? For God's sake, man!

> Barry Shields: No. Actually, it was MacMillan's.

> John Bosworth: You son of a bitch.

And then later, when they hire Cameron Howe as the programmer to write the BIOS for their clone, there is a whole scene on her first day where Barry Shields interviews her to make sure everything is legal, and that she wasn't involved in the reverse engineering.

> Barry Shields: Answer honestly. This is for legal record. False answers put you at risk of perjury, you understand?

> (Cameron nods)

> Barry Shields: I'm sorry, you have to answer "yes" or "I do."

> Cameron Howe: Oh, yes, I do.

> Barry Shields: Have you ever attempted to disassemble or deconstruct any product manufactured by International Business Machines, more commonly known as IBM?

> Cameron Howe: Uh, no, I have not.

> Barry Shields: Have you ever attempted to reverse engineer any product or equipment made by IBM?

> Cameron Howe: No, I have not.

> Barry Shields: Have you ever attempted to reverse engineer any microchips, microcode, or any computer hardware while under the employ of a business or corporation?

> Cameron Howe: No, I have not.

> John Bosworth: Well, welcome to the tiniest, leakiest lifeboat you ever tried to paddle to shore in.

The rest of the season highlights how Cameron is placed in a "clean room" (aka the storage closet) without looking at the binder containing the dumped BIOS.