A computing system for a data processing apparatus which carries out data processing using a formula. The system includes a link data file for storing formulas which are described by command names assigned to data elements and operation symbols which define operation between the command names, an actual data file for storing actual data in correspondence with the command names in the formulas managed by the link data file, and a computing file for operation processes for computing the operation contents of the operation symbols in the formulas managed by the link data file. A process is provided for specifying a requested formula which is to be computed by referring to the link data file in response to a computation request, reading from the actual data file the actual data corresponding to the command names in the specified formula and reading from the computing file the operation processes corresponding to the operation symbols in the specified formula, and carrying out operations of the operation processes read from the computing file with respect to the actual data read from the actual data file.

A graph display apparatus wherein a dynamic invention has the following arrangement. A dynamic graph key in a key input unit is operated by a user and a functional formula subjected to graph calculation and a change range and a change pitch of a coefficient value present in the functional formula input using numeric. symbol keys are stored in a formula register in a RAM (Random Access Memory). When an execution key is operated in a state wherein a coefficient change speed is stored in a register, the coefficient value of the functional formula is sequentially replaced within the change range at the change pitch. Graphic data of the functional formula and corresponding graph formulas with the changes in coefficients are sequentially stored in a plurality of video memory areas in a VRAM (Video Random Access Memory), and graphs and corresponding graph formulas for the changes in coefficients are sequentially read out in accordance with the coefficient change speed to be sequentially switched and displayed on a display unit. When the coefficient present in the formula is changed as a parameter, the graphs corresponding to the formulas are sequentially displayed, thus easily grasping the graph change state with the change in coefficient.

There are provided an electronic computing apparatus having a graph displaying function and a graph displaying method which allow an optimum graph to be quickly displayed. A graph is displayed on a display based on data for displaying the graph inputted from a key input section or the like. When one numeric key selected from among a plurality of numeric keys is specified by a predetermined number of times, a quadrant corresponding to the numeric key is selected from a quadrant selection table and a scale corresponding to the specified number of times is selected from a quadrant scale selection table, redisplaying a part of the graph existing in the selected quadrant on the selected scale. Thus, a desired graph may be quickly displayed by selecting the quadrant and scale of the displayed graph.

A graph displaying device and method whereby when functional expression data for producing graphs and the conditions of displaying the graphs are set, graphs for functional expressions data input in accordance with the conditions are displayed in corresponding colors on a display. First, functional expression data and corresponding color data which designate display colors of the graphs are input in corresponding relationship. In addition, range data which display coordinates and color data designating display colors of coordinates involved in the range data are input together. In response to this operation, the graphs for the input functional expression data are produced with the range data to which the color data are designated, the last-mentioned color data corresponding to color data which correspond to the functional expression data. The produced graphs and the coordinates are displayed in the corresponding designated colors.

A function graphing method for detecting discontinuities. The method involves scanning piecewise linear segments of the function graph and detecting large changes in the angle between segments. When such changes in angle are found, a bisection routine is performed to determine whether a discontinuity exists between the end points of a segment.