IL is a low level textual language which provides capabilities for effective PLC programming. It is based on individual instructions which define one operation per instruction. Besides the variables listed explicitly as arguments for an operation, the actual value of the accumulator is used as an additional implicit argument.
The result of an operation is also stored here after the execution of the appropriate instruction, thus providing a link between a preceding instruction and one that follows.
An Instruction List program is internally structured as an assembly of networks.