Part of the troff suite of Unix document layout tools, tbl is a preprocessor that formats tables. Mike Lesk is the original author of tbl. Like the main troff program, it uses command lines interspersed with data to be printed. Because of the nature of tabular data having rows and columns, tbl commands also intraline delimiters for fields and to indicate where to draw lines. The last formatting ends a period indicate cell data follows. The data comes next, one line per row, with tabs (by default) separating cells. Finally a line containing just .TE ends the table.