More information about currency symbols
A currency symbol (or currency sign) is used to identify and shorthand a currency name. More than one hundred currency symbols are used around the world. The most commons are the Dollar, the Euro, the Rupee and the Pound. All of them are widely used in there respective country (or economic zone, like the Euro zone), for business to customer commerce. But for official announcements and publications, at the international level, the currency codes are generally prefered over the currency symbols. Indeed, how to distinguish between the American Dollar and the Canadian dollar, that use the same symbol ($). The Egyptian Pound and the English Pound for instance, lead to the same ambivalent issue.
Nowadays, the international currency code is prefered over the local currency symbol. For instance, Indian Rupee symbol (₹) is replaced by the INR code. These official currency codes are now recognized by all official organisations, and are normalised by the ISO 4217 Currency Codes document. It's a very useful source of information that is regularely updated and maintained by the ISO organisation. The complete document is available here: ISO 4217 Currency Codes Resources.
From a more technical point of view, at the beginning, not all the currency symbols were available in the characters sets used in the IT world. This is why currency codes are also prefered for technical reasons. But nowadays, nearly all currency symbols are available in the UTF-8 character set for instance. They can be displayed using their corresponding hexadecimal code, that is given in the table available on the main page of this website, dedicated to currency symbols and currency codes: Currency Symbols table.
Most of the current currency symbols are derivated from historical symbols. For instance the dollar and peso symbols originated from the mark employed to denote the Spanish real de a ocho. And the libra, the Roman pound of silver, gave birth to an L, used to designate the Pound and the Lira. This last currency, the Lira (and most of the historical European currencies), has been replaced by the Euro: the creation of common economic zones tends to unifiy and to reduce the number of currencies used in the world.