The term “Coded Welding”, ”Code Welding” or “Welding Codes” means that the person who says they are a “coded welder” has taken an exam in a welding process using a certain method. (Welder Approval Test). For example, think of the situation of learning to become an aeroplane pilot. Once you have qualified as a pilot you then have to take type approval tests to be able to fly different types of aeroplane.
The same applies to welding codes. If you wanted to work for a company that installed stainless steel tubing in factories then you would probably train for coding using TIG welding for stainless steel tube in an all positions 6G configuration. You need to consider 1.Process. 2.Material. 3.Thickness. 4.Type of joint.5.Position (Difficulty). Usually, 1G is the easiest and 6G the hardest.