text: nonlinear programming?   a nonlinear program (nlp) is a problem that can be put into the form      minimize   f(x)      subject to gi(x)  = 0    for i = 1, ..., m1       where m1 >= 0                hj(x) >= 0    for j = m1+1, ..., m     where m >= m1  that is, there is one scalar-valued function f, of several variables (x here is a vector), that we seek to minimize subject (perhaps) to one or more other such functions that serve to limit or define the values of these variables. f is called the "objective function", while the various other functions are called the "constraints". (if maximization is sought, it is trivial to do so, by multiplying f by -1.)  because nlp is a difficult field, researchers have identified special cases for study. a particularly well studied case is the one where all the constraints g and h are linear. the name for such a problem, unsurprisingly, is "linearly constrained optimization". if, as well, the objective function is quadratic at most, this problem is called quadratic programming (qp). an even more special case of great importance is where the objective function and the constraints are entirely linear; this is called linear programming (lp) and is discussed in a separate faq list. another important special case, called unconstrained optimization, is where there are no constraints at all.  one of the greatest challenges in nlp is that some problems exhibit "local optima"; that is, spurious solutions that merely satisfy the requirements on the derivatives of the functions. think of a near-sighted mountain climber in a terrain with multiple peaks, and you'll see the difficulty posed for an algorithm that tries to move from point to point only by climbing uphill. algorithms that propose to overcome this difficulty are termed "global optimization".  the word "programming" is used here in the sense of "planning"; the necessary relationship to computer programming was incidental to the choice of name. hence the phrase "nlp program" to refer to a piece of software is not a redundancy, although i tend to use the term "code" instead of "program" to avoid the possible ambiguity.   the sites below are quite good. if you want a career in operations research or retailing management, nlp is a gr8 plus to learn