The document summarizes key aspects of a programmable logic controller (PLC) including its input and output process images, marker memory, data memory, addressing symbols, types of timers and counters. The input process image stores status of input points from the base and expansions. The output process image updates and stores status of output points per the logic scan. Marker memory holds intermediate results in the application program and data memory holds intermediate results and function block instance data. Addressing symbols are described for normally open, normally closed, output coils, reset output, and set output. Timers include on delay, off delay, and pulse and counters include up, down, and up/down with unlimited numbers and maximum preset values described.

3.  Input Process Image:
The Processor scans all the input points from base as
well as expansions in input scan & stores the status
in input process image.
%IB0 to %IB31
 Output Process Image:
The processor updates the status of output points as
per the logic scan & stores the updated status in the
output process image.
%IB0 to %IB31

4.  Marker Memory
Marker memory holds the intermediate results in the
application program. This is addressable global
memory.
%MB0 to %MB3999
 Data Memory
Data memory holds the intermediate results and
function block instance data. This is memory is
addressed by user defined symbolic name.

8.  Addressing of Symbols:-
 ----||----- NO NORMALLY OPEN
 ----||---- NC NORMALLY CLOSED
 ----( )---- OP O/P COIL
 ----( R )---- RESET O/P RESET
 ----( S )---- SET O/P SET

9.  Types Of Timer:
1. TON - On delay Timer
2. TOFF - Off Delay Timer
3. TP - Pulse Timer
 No. of Timers-: Unlimited
 Max Preset Value-: Around 24 days

10.  Types of Counter:
1. CTU: Counter Up
2. CTD: Counter Down
3. CTUD : Counter Up Down
 Max No. of Counters: Unlimited
 Max Preset Value: 32767