Program (console)

The company is very interested in making a comparison of the reliability of the different models it has installed.

Its models are simply named model A, model B, etc. For each model there are many separate instal- lations, identified by sequence number of 8 digits. Each elevator is uniquely identified by a serial number that starts with the model letter and ends with its sequence number.

Files have been created that aggregate the logs of many elevators:

• Each line starts with the serial number of an elevator.

• The rest of line is as per a log for one elevator:

- A U labels a time as a t_up, or a D labels a time as a t_down, followed by the time in seconds since the elevator was first put into service.

- The first line for each elavator will always indicate t_up at 0 seconds.

- The last line for each elavator is usually also a t_up, though it is possible that the log has been uploaded while the elevator is out of service, and therefore the last line is a t_down.

- A new elevator that has not failed yet may have one line for it.

• The file has been sorted by serial number and then time.

• Not all models might be represented in the file. The serial numbers might not be sequential.

• A new model might not have suffered any fail- ures yet.

The first 25 lines of file: small.txt

Another data file exists with much more data: big.txt.

Write a program that reports the comparison for all models represented in the data file in a table, reporting: the number of each model installed; the total uptime, the total number of failures, and the overall MTBF.

Example output for these two data files:

Note how the results are reported when there have been no failures, and that to make the table neat, the format of the numbers has been controlled.