How a Trading Floor Is Organized

Finance 101 covered market-making mechanics for a single stock. This chapter zooms out to the actual structure of a trading floor — the different desks, what each trades, and how they relate to each other.

The major desks, by asset class

• Cash equities: trading individual stocks — the market-making mechanics from Finance 101, applied at scale across thousands of names.
• Equity derivatives: options and other equity-linked derivatives — the products from Finance 101's options deep dive, traded and structured by a dedicated desk.
• Rates: government bonds, interest rate swaps, and other interest-rate-linked products — directly built on Finance 101's fixed-income chapter.
• Credit: corporate bonds, credit default swaps — pricing and trading the credit-spread concept from Finance 101 directly.
• FX: currency trading — spot, forwards, and FX options, built on Finance 101's FX chapter and the hedging deep dive's forward-contract mechanics.
• Commodities: physical and financial commodity products — futures, swaps, and options on oil, metals, agricultural products.
• Structured products: bespoke instruments combining features from multiple asset classes (e.g., a note whose payout depends on both an equity index and an interest rate) — built by specialists who blend derivatives pricing from multiple desks at once.

Flow trading vs. more directional risk-taking

Most of a modern trading floor is flow-driven: executing and managing risk from genuine client orders, capturing spread (Finance 101's market-making chapter) rather than making large directional bets. A smaller portion of real, regulated risk-taking happens on market-making inventory that a desk holds temporarily while managing client flow — genuine directional proprietary trading at banks is heavily restricted today by regulation in most major markets, a real, structural difference from how trading floors operated decades ago.

Front office, middle office, back office — who actually does what

• Front office: the traders and salespeople directly generating revenue and interacting with clients — the visible, client-facing roles.
• Middle office: risk management, P&L reporting, and product control — verifying trades are booked correctly and risk stays within limits (the next chapter's entire subject).
• Back office: settlement, clearing, and operations — making sure trades actually settle correctly (cash and securities genuinely change hands) after they're agreed.

A trade an equities salesperson executes for a client at 10am touches all three groups before the day is over — the front office negotiated and booked it, the middle office confirmed it fits within risk limits and priced it correctly, and the back office ensures it settles two days later exactly as agreed.

Worked example: how one desk's daily P&L actually gets built

A cash equities market-making desk buys 50,000 shares from client flow at $40.00 and sells 45,000 of them back into the market throughout the day at an average of $40.08, ending the day still holding 5,000 shares (the desk's inventory position) that closed at $40.05.

• Realized P&L (on the shares actually bought and sold): 45,000 × ($40.08 − $40.00) = $3,600.
• Unrealized P&L (on the remaining inventory, marked at today's close): 5,000 × ($40.05 − $40.00) = $250.
• Total day P&L: $3,600 + $250 = $3,850.

This same realized-vs-unrealized split is exactly what middle office P&L reporting produces every single day, for every desk, and it's the real number a desk head reviews to understand whether performance came from genuine spread capture (realized) or simply favorable marks on inventory still being held (unrealized, and reversible).