QSopt supports two ASCII formats for specifying LP and MIP problems. The formats are based on two industry standards, the MPS format and the LP format .

Both formats provide convenient mechanisms to define an LP or MIP problem, that is

• its objective and whether it should be minimized or maximized,
• the constraints with their expressions, senses, and right-hand-sides,
• the problem's variables, and their bounds, see Default variable Bounds,
• which variables are integer variables, and
• the problem's name.

The QSopt parser expects that all problems that it reads have at least one constraint and at least one variable. The objective function that it reads may be empty, that is, it may contain no terms; in such a case, the optimization routines attempt only to find a feasible solution when solving the problem.