The DirectLogic line of PLC's are sold by a company out of GA called Automation Direct.  It is a decent, low-cost PLC.  The model you have is a modular PLC, meaning it has a mounting rack, and a seperate CPU and I/O modules mounted in the rack.  The company that makes their PLC's is called Koyo, and they used to make PLC's for GE and (I think) Texas Instruments.

You can purchase the software at Automation Direct's website (DirectLogic32).  Be careful, because they sell a cheaper version that only works with their 'brick' PLC's.  I think they have a free downloadable version that only lets you develop/upload/download up to a certain amount of rungs/instructions.  They also will have comm cables, which are serial 9-pin to RJ11 jack for under $30.  This cable should work with whichever CPU model you have; DL230, 240, 250.