A data control device comprising: an execution means for executing, as an active runtime environment, one of a plurality of runtime environments (E1, E2, E3) each provided with an individual clipboard (C1, C2, C3) used for data reading and writing; a switching means for switching the active runtime environment characterized by: a decision means for, when the active runtime environment is switched by the switching means, deciding whether an item of data written to a clipboard of a runtime environment that is active before the switching should be copied to a clipboard of a runtime environment that will become active after the switching, by referring to an attribute of at least one of the runtime environment that is active before the switching and the runtime environment that will become active after the switching; and a management means for managing copying of the item of data between the clipboards (C1, C2, C3) based on a decision made by the decision means, wherein in a case where the switching means switches the active runtime environment in response to an operation performed by a user, the management means performs the copying of the item of data written to the clipboard of the runtime environment that is active before the switching, to the clipboard of the runtime environment that will become active after the switching, irrespective of the decision made by the decision means, wherein when a predetermined item of data written to a first clipboard of a first runtime environment is copied to a second clipboard of a second runtime environment, the management means records that the predetermined item of data is copied to the second clipboard, and in a case where the active runtime environment is switched after the copying of the predetermined item of data, and the runtime environment that is active before the switching is the second runtime environment while the runtime environment that will become active after the switching is the first runtime environment, the copying of the predetermined item of data from the second clipboard of the second runtime environment to the first clipboard of the first runtime environment is not performed. an execution means for executing, as an active runtime environment, one of a plurality of runtime environments (E1, E2, E3) each provided with an individual clipboard (C1, C2, C3) used for data reading and writing; a switching means for switching the active runtime environment characterized by: a decision means for, when the active runtime environment is switched by the switching means, deciding whether an item of data written to a clipboard of a runtime environment that is active before the switching should be copied to a clipboard of a runtime environment that will become active after the switching, by referring to an attribute of at least one of the runtime environment that is active before the switching and the runtime environment that will become active after the switching; and a management means for managing copying of the item of data between the clipboards (C1, C2, C3) based on a decision made by the decision means, wherein in a case where the switching means switches the active runtime environment in response to an operation performed by a user, the management means performs the copying of the item of data written to the clipboard of the runtime environment that is active before the switching, to the clipboard of the runtime environment that will become active after the switching, irrespective of the decision made by the decision means, wherein a decision means for, when the active runtime environment is switched by the switching means, deciding whether an item of data written to a clipboard of a runtime environment that is active before the switching should be copied to a clipboard of a runtime environment that will become active after the switching, by referring to an attribute of at least one of the runtime environment that is active before the switching and the runtime environment that will become active after the switching; and a management means for managing copying of the item of data between the clipboards (C1, C2, C3) based on a decision made by the decision means, wherein in a case where the switching means switches the active runtime environment in response to an operation performed by a user, the management means performs the copying of the item of data written to the clipboard of the runtime environment that is active before the switching, to the clipboard of the runtime environment that will become active after the switching, irrespective of the decision made by the decision means, wherein when a predetermined item of data written to a first clipboard of a first runtime environment is copied to a second clipboard of a second runtime environment, the management means records that the predetermined item of data is copied to the second clipboard, and in a case where the active runtime environment is switched after the copying of the predetermined item of data, and the runtime environment that is active before the switching is the second runtime environment while the runtime environment that will become active after the switching is the first runtime environment, the copying of the predetermined item of data from the second clipboard of the second runtime environment to the first clipboard of the first runtime environment is not performed.