Instruction in LD

Ladder (LD) is a visual programming language defined by the IEC 61131 standard. It includes components:

Function AND - (X . Y) :
|---------| |----| |---------|    
           X      Y

Function OR - (X + Y) :
|------|---| |--|------------|
       |    X   |
       |---| |--|
            Y
            
Logical function - F=(X.Z + /Y) :
|---|---| |---| |---|----( )-|
    |    X     Z    |     F
    |---|/|---------|
         Y

Inputs :
- Instruction normally open     : --| |--
- Instruction normally close    : --|/|--
- Instruction with rising edge  : --|P|--
- Instruction with falling edge : --|N|--

Outputs :
- Coil normally open  : --( )--
- Coil normally close : --(/)--
- SET Coil            : --(S)--
- RESET Coil          : --(R)--

It allows to realize logical functions graphically:

Function AND - (X . Y) :
|---------| |----| |---------|    
           X      Y

Function OR - (X + Y) :
|------|---| |--|------------|
       |    X   |
       |---| |--|
            Y
            
Logical function - F=(X.Z + /Y) :
|---|---| |---| |---|----( )-|
    |    X     Z    |     F
    |---|/|---------|
         Y