There are two modes in which to access the samples from the NIDAQ card which are stored in an internal circular buffer. The two read modes are (1) CONSECUTIVE_MODE which will not skip any elements stored in the internal circular buffer, and (2) LASTEST_MODE which will read from the writing end of the circular buffer so that the most recent values of the sampling will be read. This program is for displaying the sensor data on screen, so the LATEST_MODE is used, but if you want to send the data to some other code for processing, you probably want to set the read mode to CONSECUTIVE_MODE.
There is one limitation to the "Easy I/O" for DAQ functions: all of the channels will be sampled at the SAME sampling rate. Stanford is missing the book describing the DAQ_* functions which could be used to do parallel sampling of channels at unrelated sampling rates.
An added feature of the allchan program is that you can
select the NIDAQ sampling voltage range independently for each
channel, so you could have -10 volts to 10 volts for a piezo sensor, while
on another channel you can sample in the range from 0 to 5 volts
for an FSR for example.