hi. I'm new here at arduino and i'm really confused as to how to program my I2C devices. I have a data logger shield from adafruit which i know has an RTC and a temperature sensor TC74A0 which also runs on I2C. I already know the sensor's address which is 74, i'm just not sure how to write the code. Will the RTC keep on running even when i begin transmission with the sensor? or is there some kind of interrupt? help please..
You didn't include any links to the products or any code, but an RTC that didn't keep running wouldn't be much use to anyone.
Post your code, post your observations, post your problems.
Looking at it from a different angle, you need simply to do two things: Make sure you have identified the correct connections - which should already have been made if you are using a shield - to the SDA and SCL and can adapt the code where necessary to these particular connections, and then start practicing with sketches that you can already find within the Arduino IDE itself and the tutorials available from the various supporters, for each individual component. You do not need to write the code for yourself, it has already been done for you.
When you have each of these sketches working correctly, you can then study that code to understand how they work, and determine how to assemble various modules to perform what you want them to do in combination. The important thing is - integrate one device at a time.
There are two important principles in using I2C. One is that as long as they have different addresses (address ranges), all I2C devices are independent and do not affect one another. The second is that in almost all cases I2C does not drive the device but is an interface while the I2C device goes about its business; unless you instruct it to change its function, it is designed to proceed, again independently, with that function.