Because using a database is too mainstream
What?
The .ivact file format is a simple text-based file format. It is similar to a HTML file and can be edited with a text editor.
Why?
Because most users won't be storing the data for long term use; therefore, using a database will be overkill for such as simple program.
Understanding the syntax
A closer look
<AC>Loan/Liabilities (Non-current)/0 <J>0000 <D>01 August 2013/Cash/1500 <D>01 August 2013/Bank/89000 <D>01 August 2013/Furniture/8500 <C>01 August 2013/Owner's Capital/99000 <DE>Start. </J>
<AC> declares that it is an account and it shows the name, type, and the opening balance of the account.
<J> declares the start of a new journal entry and the number that follows behind it represents the journal number.
<D> declares that it is a Debit entry, it shows the date, account, and the value to be debited.
<C> declares that it is a Credit entry, it shows the date, account, and the value to be credited.
<DE> declares that the journal entry has a description, it shows the description of the journal entry.
</J> declares that it is the end of the journal entry. The program will add the journal entry when it reaches this point.
The journal entry shown in the code block above is the first journal entry(No.0000) and it has 3 debit entries and 1 credit entry. The journal entry is dated 1st of August 2013 and it has a description of "Start."