how to use arduino in master and slave formation

hello, i want to use 4 arduino boards with 3 boards as slave while one as their master, so how is it possible to interface them in master slave formation, please do guide me in this regards.

Also is it possible to interface the master arduino board with the PLC ( Programmable Logic Controller), if yes, then how can i do it?

Thanks.

Why so many Arduinos? Most beginners thing this is the answer to not knowing how to program correctly.

You can use I2C to do this, examples as a master and slave are in the IDE under examples menu.

How far apparat are these Arduinos? An I2C bus is only good for about five feet.

Explaining your project more coherently might be helpful. Your use of "master and slave" might well be just loose language.

I support @Grumpy_Mike's question about the need for multiple Arduinos.

You can easily implement wireless master and multiple slaves with nRF24L01+ 2.4GHz transceivers

I don't know anything about PLCs but I suspect Googling Arduino PLC or PLC site:arduino.cc would be worthwhile.

...R