[absolutely nothing - it is good practice to put your question in the body of
the message.]
The question, given in the subject was: PLC, PIC, PLD, what is the difference between them?
A PLD (Programmable Logic Device) is an integrated circuit consisting of several AND and OR gates, and maybe flip-flops, which the user can "program" to connect in various ways. One PLD might replace a small handful of TTL logic chips.
A PIC is one of a family of microcontrollers made by MicroChip (see
formatting link
for details)
A PLC is a Programmable Logic Controller is a complete product (made by several manufacturers) intended to accept inputs from switches (and sometimes analog sources) and control various devices. These systems are used as part of industrial control systems, and normally deal with
24 volt input and output signal levels. They are usually programmed using "ladder logic".