The National Electrical Code is the bible that determines the rules of all electrical construction. Many countries share very similar rules through international trade associations, and it is easier to adopt regulations that the experts agree provide the highest degree of personal and community safety. Because of the danger of electricity around the water found in kitchens, the NEC has strict guidelines about what is and is not required.
An electric range uses a dedicated 220V circuit because of the power that it draws. The 220V wiring in an older home may end in a three-prong outlet, or a four-prong outlet in a new home. The pigtail, or the electric cable that leads from the back of the oven to the outlet, is installed at the home to match the proper type of outlet. In some homes, the builder may design the outlet so that the oven wires are permanently attached to the electrical system.
The determining factor for any oven is the manufacturer's installation instructions. If the instructions say the oven cannot be hard wired, then it overrides any code that allows it. If the instructions say it can be hard wired, then the local code will also accept it. If the outlet is a three- or four-prong one and you want to hard wire the oven, it is a simple, few-minute task to take the outlet out and convert it to a hard-wired one.
Electricity is a fickle helper, able to turn instantly from a friend that powers our tools and entertainment centers to a raging beast that causes fires and kills people with shocks. Rewiring any outlet or hard wiring appliances is dangerous unless you know what you are doing, and a 220V outlet is far past really dangerous. Getting a 110V shock may or may not not kill you, but few survive a jolt from a miswired or runaway 220V circuit. If you are not confident in hard wiring a stove, seek professional help.