File locking is a mechanism that restricts access to a computer file by only allowing one user or process access at any specific time. Systems implement locking to prevent the classic interceding update scenario (see race condition).
The following example illustrates the interceding update problem:
# Process A reads a customer record from a file containing account information, including the customer's account balance and phone number.
# Process B now reads the same record from the same file so it has its own copy.
# Process A changes the account balance in its copy of the customer record...
