Can any one help me name two different alternatives to PLC systems available and detail the capabilities and typical uses of each alternative?

Basically the acronym PLC is Programming Logic Control which was used by the method of relay ladder logic with switches. After the rapid grouth of industrial revaluation additional features had required, those were satisfied with microcontroller low level languages. and the advanced method is embedded 'C'.  

Printed circuit boards (PCB) and relay logic are two options in replacing a PLC. 

1) PCB- is a non flexible system meaning that it will take the user time to change or add conditions that effect the system.

2) Relay logic- this is a outdated system and will take up a lot more space and wiring.

ABB-RS LOGIX

SIEMENS-SCHEMATIC MANAGER S700