Does a dishwasher have an embedded computer?

Linux

This mostly depends on the kind of dish washing machine you own and what you consider a 'computer'.

If its an older machine, its quite possible that the machine 'logical' or controlling device is mechanical working off of timers, springs etc. It could be argued this does 'compute' (the first computer ever made by Babbage was mechanical) however in the modern sense (or in my opinion), a computer is a device that contains some sort of centralized processing unit (CPU) that does the complicated math/'thinking' for other functional devices that actually perform tasks. When a device can be programmed to perform/control multiple tasks, you're in the realm of computer.

Today, many appliances from your fridge to your dishwasher do have a computer of some sort in them. Lots of appliances actually run stripped down versions of Linux, a popular open source operating system like Windows on your own computer. So if your dishwasher is relatively new, theres a very good chance it has, or essentially is a computer with an aquatic device attached to it that it controls.

Sorry if this means you lost a bet.