Engineering tool program and engineering tool

An engineering tool program for causing a computer to function as an engineering tool that monitors a programmable logic controller configured by a plurality of units and forming a control system, the engineering tool program causing the computer to function as:

• a content-data memory to store data in which content classes indicating classifications of content data to be displayed by the engineering tool and types of monitor screens that display the content data are associated;
• a content-relation managing circuitry to store content relation management data indicating a hierarchical relation of layers among different content classes;
• and
• a display controller to change, after first operation is performed, a monitor screen being displayed to a monitor screen corresponding to a content class of an immediately subordinate layer on the basis of the content relation management data and change, after second operation is performed, the monitor screen being displayed to a monitor screen corresponding to a content class of an immediately superordinate layer on the basis of the content relation management data, wherein the content relation management data includes contents of the units, contents of variables indicating states of the units, and contents of sequence programs in which the variables are used.