COL variable;
For the sparse input format, the COL statement specifies a character variable in the problem data set that contains the names
of the columns in the model. Columns in the model are either structural variables, right-hand-side vectors, right-hand-side
change vectors, or a range vector. The COL variable must be a character variable. If the COL statement is omitted, the LP
procedure looks for the default variable name _COL_
.