Features Of Structured Programs - Mitsubishi Electric MELSEC Q Series Programming Manual

1.2

Features of Structured Programs

This section explains the features of structured programs.
Structured design
A structured design is a method to program control content performed by a programmable controller CPU, which are divided
into small processing units (components) to create hierarchical structures. A user can design programs knowing the
component structures of sequence programs by using the structured programming.
The following are the advantages of creating hierarchical programs.
• A user can start programming by planning the outline of a program, then gradually work into detailed designs.
• Programs stated at the lowest level of a hierarchical design are extremely simple and each program has a high degree of
independence.
The following are the advantages of creating structured programs.
• The process of each component is clarified, allowing a good perspective of the program.
• Programs can be divided and created by multiple programmers.
• Program reusability is increased, and it improves the efficiency in development.
Multiple programming languages
Multiple programming languages are available for structured programs. A user can select the most appropriate programming
language for each purpose, and combine them for creating programs. Different programming language can be used for each
POU.
Name
ST (structured text)
Structured ladder/FBD
For outlines of the programming languages, refer to the following section.
Page 23 Programming languages for POUs
For details on each programming language, refer to the following chapter.
Page 73 WRITING PROGRAMS
The ladder/SFC languages used in the existing GX Developer and Simple projects of GX Works2 can be used.
For details on writing programs, refer to the following manuals.
 Programming manuals for each CPU
Improved program reusability
Program components can be stored as libraries. This means program assets can be utilized to improve the reusability of
programs.
1 OVERVIEW
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1.2 Features of Structured Programs
Structured ladder
FBD
Description
A text language similar to C language, aimed for computer engineers.
A graphic language that is expressed in form of ladder by using elements such as contacts
and coils.
A graphic language that is expressed in form of ladder by connecting elements such as
functions and function blocks with lines.