I have never used octal numbers in my code nor come across any code that used it. I bet you have. According to the standard, numeric literals which start with zero are octal. This includes, trivially, 0. Every time you have used or seen a literal zero, this has been octal. Strange but true.
If you are making child support payments in Texas, the law generally requires you to do so until your child turns 18, which is the age that marks adulthood in the state, or when he graduates from high school -- whichever comes later.
You will need to notify the court to ask that your child support obligation stop. If you owe back support, the court can order that you continue paying the back support even if the court says your child is emancipated. My child just turned 18.