noob question

Hello everyone. I'm a computer programmer and I consider myself very good with math and numbers in general, as long as the words debit, credit, financial or the such are not around. A simple monetary sign
will make me go nuts, if not stupid. Shame on me; my father was a well know CPA in my country. I'm currently involved in a small project that includes some basic accounting knowledge. I think that, for most, I understand the bare basics of the accounting equation and the reasons for the double entry system and here is my doubt: In a double entry accounting system, "the nature of each account and, of course the involved entries (or transactions) determine whether or not an account's final balance is debit or credit"[a] so, if we put each account in the right position within the accounting equation we should get it balanced just by adding each account's individual balance without the need for more information.
BUT (I had lots of conversations about accounting with my father which always ended up in some Scotch sipping after a heated discussion)
1) In a computer system he had at his office, I remember that besides the fact that they had to indicate whether or not each entry was a debit or credit as expected; when they created a each account of the accounting code they had to indicated whether or not such account was a debit or a credit (Except for some very, very few exceptions he always used hierarchic code systems) . Does that make sense?
2) I cannot recall the specific examples he gave me but I seem to recall that, even though [a]; for at least some accounts, when placed within the accounting equation, it was necessary for them to be considered as opposites (debits as credits or vice-versa).
Can someone please try to clarify these doubst for me as if I was 7 years old?? Thanks a lot in advanced!!!
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Sounds like you are talking about what are called "contra accounts".
Accumulated depreciation is a contra account. It's an asset account that would always have a credit balance in it.
Allowance for doubtful accounts (where you would write-off bad debt) is a contra account of the receivables.
--
Paul Thomas, CPA
www.paulthomascpa.com
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