Many memory systems group bits together into multiples of eight called bytes. A more convenient grouping is by fours, which requires just two digits. The point to keep in mind is that octal and hex are just representations of the same binary pattern and any action to any one bit of the number will change that value in every numbering system. Decimal has no easy translation between a bit change and a number and you should entirely avoid using it when programming embedded systems. Also, even though computers can start counting from zero, don't make your customer also count this way.
People start counting from one.
Enough of the simplicity. Computers are generally very slow in doing multiplications and divisions and therefore you should try to avoid these instructions whenever possible. Most computers allow operations on the individual bits of a number such as setting and clearing. For a computer without direct bit control, the 'or' and 'and' operations are synonymous. You can easily relegate other tasks to bit manipulations.