Arduino board has a microcontroller called Atmega328. I wonder if it is CMOS or TTL. I dont know how to understand it from the datasheet. Second question is on the Arduino board there are other chips. Are they all TTL or CMOS? How can I know?
All the key facts about a chip should be contained in its datasheet. This should always be your first port of call when researching things.
Search for "CMOS". First hit is page 5:
"The ATmega48PA/88PA/168PA/328P is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture".
Bonus answer: a quick look at the Arduino UNO schematic shows three different voltage regulators, and an LM358D used as a comparator, all of which are considered "analog" parts and neither CMOS nor TTL.