Files (Cambridge (CIE) AS Computer Science): Exam Questions

An algorithm will output the last three lines from a text file Result.txt

The lines need to be output in the same order as they appear in the file.

Assume:

• Three variables LineX, LineY and LineZ will store the three lines. These are of type string and all three variables have been initialised to an empty string.

• The file exists and contains at least three lines.

The algorithm to output the lines is expressed in eight steps.

Complete the steps.

1. Open the file ...........................................................................

2. Loop until ...........................................................................

3. ........................................................................... and store in ThisLine

4. Assign LineY to LineX

5. Assign LineZ to LineY

6. Assign ThisLine to LineZ

7. After the loop, ...........................................................................

8. Output LineX, LineY, LineZ

The requirement changes, and the algorithm will now output three lines from the file, starting from a given line number.

The modified algorithm will be implemented as a function which will:

• be called with an integer parameter representing the given line number

• output three lines, starting at the given line

• return TRUE if the 3 lines are output, or FALSE if it was not possible to output the 3 lines.

Describe the changes that need to be made to steps 2 to 8 of the algorithm given in part (a).