Ladder circuit editing system

A ladder circuit editing system for inputting and editing a sequence program for a program controller in the form of a ladder diagram comprising:

• an unavailable area for storing a plurality of previously stored circuit patterns of circuit elements;
• an available area for storing a circuit pattern inputted by an operator, said inputted circuit pattern comprises circuit elements;
• circuit pattern extracting means for making a comparison between a circuit element of the circuit pattern stored in the available area and a corresponding circuit element contained in one of the plurality of the previously stored circuit patterns from the unavailable area, and extracting from the plurality of previously stored circuit patterns an extracted circuit pattern in which the comparison indicates an agreement between the compared circuit elements;
• display means for displaying the extracted circuit pattern on a screen;
• and
• copying means for copying the extracted circuit pattern into said available area in response to another input by the operator.

A method for inputting and editing a sequence program for a program controller in a form of a ladder diagram, the method comprising:

• pre-storing a plurality of circuit patterns in a first storage area;
• inputting a new circuit pattern;
• storing the new circuit pattern in a second storage area;
• comparing the stored new circuit pattern with each of said pre-stored plurality of circuit patterns;
• extracting each circuit pattern from said pre-stored plurality of circuit patterns that matches the stored new circuit pattern;
• displaying said each extracted circuit pattern on a screen;
• selecting said each displayed circuit pattern by an operator;
• and
• copying the selected circuit pattern into said second storage area,
• wherein said comparison is performed by comparing each circuit element of the new circuit pattern with a corresponding circuit element from said each circuit pattern of said stored plurality of circuit patterns.