Increasing importance is being attached to the idea of measuring software characteristics. This paper deals with following things. First, a relation of program and flow graph is discussed. It describes a theoretic complexity measure and illustrates how it can be used to manage and control program complexity. Second, cyclomatic complexity measure is discussed. The complexity is independent of physical size and depends only on the decision structure of a program. Third, consider a knot which defines crossing point and provide the ordering of the nodes to make the transition from a two dimensional graph to a one dimensional program. A program modules that can improve FORTRAN IV program text is tested by knot counting and its control complexity is improved.