READPRN is generally preferable to READ. When the data values are regularly listed out in columns, READPRN brings the data into Mathcad in a readily accessible form.
If some lines in a data file have more data values than others, data values may be missing. Use a text editor to replace the missing values with zeros before you use READPRN.
READ is required for files in which numbers for a single variable are scattered across several lines in the file. This includes files created by the WRITE function, in which there are as many numbers on each line as will fit
WRITEPRN generally produces more readable files than WRITE because the data values are neatly lined up in rows and columns. However, WRITE produces smaller files than WRITEPRN because it doesn’t have to add spaces to line up the numbers.
Use WRITE instead of WRITEPRN when you want to crowd as many values as possible into a small data file. WRITE creates a data file with only one space between each value and the next.