engine/electronic control unit...
it senses the airflow amount, the accelerator position, and the exhaust oxygen content and then calculates the precise amount of fuel needed at each injector, and fires the injectors accordingly... thats something very basic...
you know as a student google should be your best friend and soul mate 
i will repeat again.. you must see a swapped car with your own eyes. check the mounting points of each engine. then check the mounting points of a stock car.. check the length and dia of the axles.. just to figure out what you can fit in it...
to some extent a preludes parts will fit in a civic..
all the engines you mentioned have their own ecus..