The SWIFT code replaces old mail, telegraph and telex systems
Answer
The SWIFT system has replaced old financial communications methods, such as mail, telegraph and telex, which were expensive and slow.
The main SWIFT centre in Belgium hosts specialized servers that communicate with corresponding computers provided to the member banks. This is via a unique SWIFT code.
If one of the system bank members send any financial or non-financial message, the system will process it on special forms. These will then be sent to Belgium and back to the sending bank, a number of times, and will only be retrievable by the receiving bank if the code exchange is successful.