Today in History: Decimal Day 1971

Under the old currency of pounds, shillings and pence, the pound was made up of 240 pence (denoted by the letter d for Latin denarius and now referred to as "old pence"), with 12 pence in a shilling and 20 shillings (denoted by s for Latin solidus) in a pound. Especially in an era before widespread computer use, monetary calculation, such as adding up sums of money, was more complicated than with a decimal currency. Tourists were also confused by coins such as the 'half-crown' (worth two shillings and sixpence, or one eighth of a pound). The loss of value of the currency meant that the penny, with the same diameter as the U.S. half dollar, was of relatively slight value (the farthing, worth one-quarter of an old penny, had been demonetised in 1960).

For further details of the currencies before decimalisation, see British pre-decimal system and Irish pre-decimal system.

Source: encyclopedia.thefreedictionary.com