Then by your definition consoles are computers:
- they take input from the user: All the button presses on the controllers are detected by the console as input
- They compute with the given information: The game needs to calculate the new position for your character from its previous position and current input, or whether that enemy touching means game over
- They supply the output: With colorful graphics, but output nontheless
Consoles are just a specialised computer. The difference is that hardware/software it includes is geared towards providing entertaintment.
I think what you meant was that consoles are different from PCs, those are expected to do whatever the guys sitting in front wants to do, as long as the software has the capability to do so. It's like a tool, or more like an array of tools, it just does the job you want it to do. Consoles tend to fail at that (because they're not designed for it).