PURPOSE: To improve the efficiency of program development by allowing respective program engineers to use plural display terminal equipments exclusively.

CONSTITUTION: A program engineer 4-1 uses two display terminal equipments 6-1a, 6-1b. One display terminal equipment 6-1a is made waiting state under a condition that a compile list formed after editing and compiling operation has been displayed and stored. The other display terminal equipment 6-1b executes the editing operation by using display information on the display terminal equipment 6-1a. In addition to the improvement of the operation efficiency and productivity for program development, uselessness of operation on the way of program development, printing paper, etc. can be removed.