IMF Urged to Honour G20 Pledges: Where does the Money come From?

The IMF is coming under pressure to act more quickly in securing the additional $500 billion pledge at the recent G20 summit to help emerging market economies that have been battered by the global downturn.

The IMF has responded by saying that government legislatures, including the US Congress have not been forthcoming with authorisation for the money to be withdrawn.

It seems to me that it is possible that G20 leaders returning home have experienced what some people have experienced waking up the morning after a boozy night thinking, what have I done? Of course the G20 leaders were influenced by the rush of international cooperation as oppose to the intoxication of alcohol, but it seems it may have had similar effects on their senses and financial inhibitions.

Another thing occurs to me, despite the fact that we are in a global downturn, and this, after several years of the US and UK fighting costly wars, the two governments are still able to throw huge sums of money about, for bank bailouts, and stimulus plans. Where does all the money come from?

The digital age has led to money becoming such a fictional entity that, for governments and banks at least, exists only on computer monitors. Who keeps a track of all this imaginary money? Isn't it possible that zeros can be added and/or taken away at the push of a button and no one would know?