Is using a credit card safer and more convenient than carrying cash or checks?

Yes and no. Credit cards are more convenient when you need something, or you can't pay for something (at that moment) with cash. With a credit card, you can keep buying, but with money - once you're out of cash, you can't buy anymore.

However, it's not because in the long-run, you have to pay via cash anyways (referring to having to pay creditors), don't forget interest!