A DBA can be highly beneficial for business marketing, but setting up bank accounts in the name of a DBA rather than in the legal name of the individual or entity that owns the business can be complex and require documentation proving that you have a right to use the business name.
Most businesses use double entry accounting, a system in which every financial event causes two transactions, a debit in one account and an equal offsetting credit in another account. When a company establishes an accounting system, it must choose to use either a single entry system or a double entry system.
In languages like C and FORTRAN (where a double is called double precision), a double is typically understood to have twice the number of bits as a float. This isn't always true, although a double will always have at least as many bits of precision as a float in any sane implementation.