1. What's the advantage on to use, for programming of PLC systems, the Linguagem of Comandos Elétricos (Electric Commands Language) - LCE, conversely to program visually, drawing directly in the ladder diagram or in function blocks diagram?
The principal advantage is the easiness of programming, maintenance and management of the obtained PLC control programs, in proportion they are getting more and more complex. Kept in mind the right sense of proportion, this facility is similar to one obtained with the use of silicon compilers (for example, by way VHDL - Very High Speed Integrated Circuit Hardware Description Language) converselydrawing straightly digital electronic circuits.
Another positive point is the aggregation of semantics or textual significance to the control programs in LCE, with the proper text of source program constituting its better documentation, adding meaning and structure that are difficult to attain into any diagram: imagine yourself on the telephone, attempting to transmit by way of speech the ladder diagram with the lot of complexity ...
On any medium that, by technical impracticability, or matters on economy of resources, we need to transmit, store or work the PLC program into form of pure text, the alternative is the list of instructions languages - IL (Instruction List), adaptation of traditional programming language, the Basic, C, Pascal, etc., (into Structured Text - ST), or use of dedicated and specific high-level languages.
The IL languages are low-level, the the assembly, with all problems of semantics, legibility, expressively and understanding associated to all low-level languages. In other hand, the traditional languages attend to general purposes at programming of the computers, they aren't fitting very perfectly to the specific needs and requirements of the codification of control programs. Dedicated and specific high-levellanguages for PLC systems, like LCE, intend supply this lacuna.