Most of the programs which expect table data input can read either standard input or input in one or several files. These programs will try to read stdin unless you type the filename(s) on the command line without the above hyphens. (If the program sees a hyphen, it reads the next character as an instruction; if an argument begins without a hyphen, it tries to open this argument as a filename). This feature allows you to connect programs with pipes if you like. If your input is ASCII and has one or more header records, you must use the -–H option. The number of header records is one of the many parameters in the .gmtdefaults file, but can be overridden by -Hn_header_recs. ASCII files may in many cases also contain sub-headers separating data segments; see Appendix B for complete documentation. For binary table data no headers are allowed.