A chemistry department stores pH results from a river survey in a file. For each sample, a student enters a location code and a pH value. The program should...
Question 1 Report
A chemistry department stores pH results from a river survey in a file. For each sample, a student enters a location code and a pH value. The program should display a message if the pH value is not between 0 and 14, then allow the student to enter the value again. A later program reads the file to draw a graph of pH against location.
(a) Explain why the range test is appropriate for the pH input. [2]
(b) State one output device that could display the message. [1]
Table 1 shows part of a comma-separated file used by a parcel depot. The dispatch program reads each line, calculates the total mass for a delivery route and then displays the route number and total. Staff must be able to add new parcel records without deleting records already collected during the shift.
| ParcelID | Route | Mass (kg) |
|---|---|---|
| P1048 | N3 | 2.6 |
| P1049 | N3 | 1.4 |
| P1050 | W1 | 3.2 |
(a) When processing the first two records, calculate the displayed total mass for route N3. [1]
(b) State the file operation used to add a new record while retaining the existing file contents. [1]
(c) Explain why a comma is useful as a separator in this file. [2]
Answer Details
River pH results
- A range test is appropriate because valid pH values lie from 0 to 14. The test prevents impossible values being placed in the results file used later for graphing. [2]
- A suitable output device is a monitor/screen. [1]
Parcel-depot file
- The two N3 masses are 2.6 kg and 1.4 kg:
\[2.6 + 1.4 = 4.0\text{ kg}\]
So the displayed total for route N3 is 4.0 kg. [1] - Use append to add a new record while retaining existing file contents. [1]
- A comma separates the individual fields in each record. The program can therefore split the line and read the route and mass independently. [2]
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