The genome is littered with old copies of genes and experiments that went wrong somewhere in the recent past – say, the last half a million years. This code is there but inactive. These are called the ‘pseudo genes’.
Furthermore, 97% of your DNA is commented out. DNA is linear and read from start to end. The parts that should not be decoded are marked very clearly, much like C comments. The 3% that is used directly form the so called ‘exons’. The comments, that come ‘inbetween’ are called ‘introns’.
These comments are fascinating in their own right. Like C comments they have a start marker, like /*, and a stop marker, like */. But they have some more structure. Remember that DNA is like a tape – the comments need to be snipped out physically! The start of a comment is almost always indicated by the letters ‘GC’, which thus corresponds to /*, the end is signalled by ‘AG’, which is then like */.
However because of the snipping, some glue is needed to connect the code before the comment to the code after, which makes the comments more like html comments, which are longer: \’‘ the end.