Specifications

1.4 Features of Structured Programs
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OVERVIEW
1.4 Features of Structured Programs
This section explains the features of structured programs.
(1) 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.
(2) 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.
Table 1.4-1 Programming languages that can be used for structured programs
For outlines of the programming languages, refer to the following section.
Section 4.2.7. Programming languages for POUs
For details on each programming language, refer to the following chapter.
Chapter 5. 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
(3) Improved program reusability
Program components can be stored as libraries. This means program assets can be utilized
to improve the reusability of programs.
Name Description
ST (structured text) A text language similar to C language, aimed for computer engineers.
Structured ladder A graphic language that is expressed in form of ladder by using elements such as contacts and coils.
FBD
A graphic language that is expressed in form of ladder by connecting elements such as functions and
function blocks with lines.