What Is PLC Data Type?


Heather Bennett

What Is PLC Data Type?

In Programmable Logic Controllers (PLCs), data types are an essential concept to understand. Data types determine the nature of data stored in variables and how they are processed by the PLC. By using different data types, programmers can efficiently handle various types of information, such as numbers, text, and boolean values.

Why Are Data Types Important in PLC Programming?

Data types play a crucial role in PLC programming for several reasons:

  • Data Integrity: By defining specific data types for variables, the PLC ensures that only compatible values can be assigned to them. This prevents errors and enhances the reliability of the control system.
  • Memory Allocation: Different data types require varying amounts of memory space.

    By selecting appropriate data types, programmers can optimize memory usage and improve overall system performance.

  • Data Manipulation: Each data type has its own set of operations that can be performed on it. For example, arithmetic operations are suitable for numeric data types, while string manipulation functions work with text-based variables. Proper selection of data types allows programmers to perform the necessary calculations and operations on the given information.

Commonly Used Data Types in PLC Programming

PLC programming languages typically support a range of common data types:

Numeric Data Types

  • Integer: Used for whole numbers without decimal places. Examples include -32768 to 32767 (16-bit) or -2147483648 to 2147483647 (32-bit).
  • Floating-Point: Suitable for real numbers with decimal places.

    Commonly used for measurements and calculations requiring high precision.

  • BCD (Binary-Coded Decimal): Used to represent decimal numbers using binary-coded digits. Each decimal digit is represented by a four-bit binary number.

Boolean Data Type

The boolean data type is commonly used in PLC programming to represent two states: true or false. It is useful for controlling logic flow and making decisions based on conditions.

String Data Type

In addition to numeric and boolean data types, PLC programming languages also support the string data type. Strings are used to store alphanumeric characters, such as text messages or device identifiers. They have a fixed length and can be manipulated using various string functions.


Data types are fundamental in PLC programming as they define the characteristics of variables and how they are processed. By selecting the appropriate data types, programmers can ensure data integrity, optimize memory usage, and perform operations specific to each type. Understanding the different data types available in PLC programming is essential for developing efficient and reliable control systems.

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