The differences are:
Output mode | Append mode |
It is an overwrite mode. | It is an add mode. |
It writes data into a file. | It adds data into an existing file. |
If the data file exists, it overwrites the previous data and writes new data from the beginning of the file, and if the data file does not exist it creates a new data file. | If the data file exists, it adds new records in the data file. If the data file does not exist, it creates a new file with the same name. |