LabVIEW
The best way to save data in my situation
If you are writing a Text file, then you are writing data as strings. If your numbers are integers, you convert the integers to strings (say, the number "23" to the charcters "2" (42 in hex) and "3" (43 in hex). If you just write this out with nothing else, then when you follow by writing, say, the number "45", you'll end up with the string of charcters "2345".
So you need to separate your characters when you write out text. One way is to write a "separator" character -- comma and Tab (Hex 😎 are common choices. Files using commas as separators have a special name -- CSV (Comma-separated Variables), a format that Microsoft Excel knows how to read.
Another common separator is the New Line character-or-characters. This is a little bit OS-dependent, but LabVIEW can generally read them all.
When you use the LabVIEW Write Text function, you might notice it (sometimes) has a two-arrow symbol in the lower-right corner. This stands for Carriage Return (the arrow that goes down-and-left) and Line Feed (the arrow that goes down). With this on, each call to this function should write a new line of text. Without it, they will all appear on the same line.
Hope this clarifies things somewhat. If you are unclear, write yourself a tiny LabVIEW routine that generates some data, convert it to strings, and try writing various (tiny) Text files and see what you get. Experimentation on your own is a good and fast way to learn some of LabVIEW's quirks.
Bob Schor
P.S. -- it's a good thing I take my own advice! My description of how to write multiple lines is not quite right. If, for example, you call Write to Text File and give it the strings "1", "2", "3", "4", "5" (generated, say, by a For loop), you'll get "12345", even though a quick read of the Help says that it will write them as lines. The trick is it writes arrays of strings as lines. The attached Snippet, in which I added "Build Array", gives me a one-column output.
Another alternative is to save your data files to TDMS. This works well for "sweep" type measurements. For example, an RF Power gain sweep.
I too am usually a fan of TDMS. It has some of the features of a database (reading values based on looking up names, not column or row indexes), it has a relatively small file size with ideally just a few kb for index information with data being stored as binary, and is generally easy to work with. It isn't the only solution, and as others have said, for quick logging a CSV is generally the easiest, with the Write Delimited Spreadsheet allowing to append data easily. Text is also a format that everyone can read without any extra tools like a TDMS viewer, or database reading tool. In your situation I'd just stick with a text file, and I'd recommend you get more familiar with TDMS and databases to best understand when to use one over the other in the future.
