Circular buffer usage

Use it when you want a double-ended queue rather than an array. Input buffers are a good use case for this (you read from one end and new data [i.e. fresh input] is added at the other end).

Lets say you have a game with a rewind functionality, where your character can travel back in time. You'll most likely have a cap on how far one can rewind. At any point in time, you'll have to know the x steps taken before the current step. Now imagine how easy this becomes with a circular buffer .

Having a circular buffer prevents you from allocating new memory.

It also prevents memory fragmentation.

Both of these problems will cause performance drops.

Any task that involving queues where performance is an issue will benefit from a circular buffer.

They are also in use in hardware and embedded programming.

Here, memory allocation (new / malloc ) is sometimes not available.

Perfect for use with producer and consumer queues as well, think chat messages and stuff like that.

Yeah, as I said anything a double ended queue is good for is ideal (as long as the queue has a fixed maximum size - although it can be resized of course. For efficiency reasons you will probably prefer a buffer size which is a power of 2 so you can use logical AND rather than modulo arithmetic to wrap the buffers).

More use-cases:

Message system (read messages from front of queue add new messages to the back of the queue).

Bubble Bobble (Puzzle Bobble? Maybe?) scrolling-type games where new tiles are added to the top of the screen and tiles are removed from the bottom of the screen.

Rewind buffer (already mentioned)

Text window with limited history (already mentioned)

Undo buffer with limited undo

etc.

I know they are used in LZMA and LZSS compression as way to create a sliding window for the algorithm and in various aspects of digital signal processing.

Circular queues are common when decoding audio, which is an example of a producer/consumer queue like Night mentioned.