1. A programmable controller, comprising: means for setting a cycle time of a cycle for one round of execution of a series of processing routines, said series of processing routines comprising a first predetermined processing routine having a start and termination and a second predetermined processing routine having a start and a termination, said series of processing routines including a block of user programs whose execution is uninterruptedly completed within one cycle, wherein said setting means includes: means for setting an instruction which specifies said cycle time; input/output relay means logically linked to said instruction setting means to control the setting of said instruction; first storage means for storing said cycle time specified by said instruction; and second storage means for storing a logic state of said input/output relay means; means for counting an execution time between the start of the first predetermined processing routine and the termination of the second predetermined processing routine which follows the first predetermined processing routine in said series of processing routines; means for calculating a time difference between said execution time counted by said counting means and said cycle time; and means for allocating said time difference to execution of the remainder of said series of processing routines subsequent to said second predetermined processing routine, when said execution time is less than said cycle time; wherein said setting means further comprises, determining means for determining in response to said state stored by said second storage means whether or not said calculating means calculates said time difference between said execution time counted by said counting means and said cycle time.