Telephone numbers are often written in following format for international dialling: +44 (0)1224 XXXX XXXX

If a P (Pause) is used it means to await a second tone at this stage.

IDD Prefix (International Direct Dialling) - Replace the + with the IDD prefix

The IDD prefix is the international prefix needed to dial a call FROM the country listed TO another country. This is followed by the country code for the country you are calling.
IMPORTANT Use the + symbol instead of the IDD Prefix in front of your country code when displaying your telephone number. The IDD prefix changes depending from which country someone is trying to call you! If you write 00 44... for example, this means that someone from the Bahamas can't call you because they have to dial 011 44... to dial the UK.
Use a + symbol instead of writing your IDD Prefix. People can't call you otherwise, who have to dial a different IDD Prefix.

Country Code

The country code is the national prefix to be used when dialling TO that particular country FROM another country. In some cases you will also need to dial a city or area code.

NDD Prefix (National Direct Dialling)

The NDD prefix is the access code used to make a call WITHIN the same country from one city/area to another and is followed by the city/area code for the local number you are calling. 
When dialling from outside the country, the NDD prefix is not be used after dialling the country code; when dialling from within the same country, the NDD prefix is required, but not the country code.
When calling a local number within the same local area, dialling the NDD prefix and the city/area code may not be necessary.