How do I interpret a record from an ASCII data file?

NSDUH data files are usually distributed as columnar ASCII files that consist of rows and columns of alphanumeric characters. Since ASCII data files are text files, they can be opened in any word processing program or Internet browser. In Stata, ASCII files are run using a formatted dictionary (.dct) file. However, the alphanumeric characters are not meaningful without the help of a codebook or setup files to identify the columns of the ASCII data file as particular variables.