Additional Activities

Activity 14-5: Read Text File by Page

Modify Read Text File Advanced.vi (from Activity 14-1) so that every time you press a NEXT PAGE button, the VI reads the next PAGE_SIZE characters from file, and when you press a PREVIOUS PAGE button, it reads the previous PAGE_SIZE characters from file. Save your VI as Read Page from Text File.vi.

• Store the file marker (the current position) in a shift register and increment or decrement it by PAGE SIZE depending on whether the NEXT PAGE or PREVIOUS PAGE button is pressed.

• Use an Event Structure for capturing button press events.

• Read the file using the file marker as the start position and page size as the number of characters.

• Make sure that you do not read before the beginning of the file (position = 0) or past the end of the file (position = end of file + 1).

Now, for extra (geek) points, use a Vertical Scrollbar control (which you learned about in Chapter 13, "Advanced LabVIEW Structures and Functions") to control the page that is read.

Configure the Scrollbar properties, as follows:

• Set Doc Min to 0 (zero).

• Set Doc Max to the file size (total number of characters).

• Set Increment to 1 (one character).

• Set Page Size to the number of characters you want in a page.