I want to use the raspberry pi for some projects, although the normal pi is too big and I want it to be as compact as possible. I thought about using the compute module(without the IO board) since it is small. I looked online to see if I could use just the module, but I couldn’t find anything that said it was possible. Is this possible?
The IO boards are used to allow simplified software development and easy access to ports while you look at interfacing the Pi into the rest of the hardware.
Once you have completed the hardware / software development it is normal to do away with the board and use the modules themselves - sometimes in a carrier board but sometimes direct to the main circuit board.
The boards do simplify tasks (such as flashing emc with code) but long term are not necessary.
Do you need them from get-go? No but you have to work out everything before you start (power / connectivity being the two main things) and only then can you get the software development going. Time savings (therefore money) are significant to use development boards as a steppingstone.
Can you use Rpi CM4 without IO Board?
The short answer is NO.
(1) For hobbyist project development, I think the most efficient way is to use the Rpi's official I/O board.
(2) There are a couple of vendors designing "Carrier Boards" for developers and hobbyists, but they are not cheaper than official Rpi.
(3) I am playing with two cheap CM4 modules. You are welcome to ask @tlfong01 to share his CM4 newbie experiences.
Appendix A - The CM4 Modules I Recommend
The official Rpi authorized shop in my city only sells two boards in small quantities, minimum order is 1. For the rest, you need to order at least 200. The three boards I am learning is the following.