Data Types & Variables

Alternative name for variable providing meaningful description of purpose.

Generic data type parameter allowing functions to accept multiple data types.

Indexed collection of same data type elements, accessed by numerical index.

Binary Coded Decimal format representing decimal digits in 4-bit groups.

Data structure packing multiple boolean flags into single memory word.

BOOL means Boolean — a single-bit data type holding TRUE (1) or FALSE (0). The most-used data type in PLC programming: every contact, coil, digital I/O point, and comparison result is internally a BOOL.

BYTE means an 8-bit unsigned data type in PLC programming, range 0 to 255. Used for status registers, packed I/O modules, and as a building block for larger data types.

Single character data type for storing individual ASCII characters.

Fixed value that cannot be changed during program execution.

Siemens-specific memory area for storing structured data and function block instances.

Calendar date representation without time component.

Combined date and time stamp for event logging and scheduling.

DINT means Double Integer — a 32-bit signed integer in PLC programming, range −2,147,483,648 to +2,147,483,647. Default integer type for counters, encoder positions, and most modern PLC arithmetic.

DWORD means Double Word — a 32-bit unsigned data type in PLC programming, range 0 to 4,294,967,295. Used for bit-packed flag registers, IPv4 addresses, and large positive integers.

User-defined type with named constants representing discrete values.

Number representation with fixed decimal point position for fractional values.

Number format allowing variable decimal position for wide range representation.

INT means Integer — a 16-bit signed integer in PLC programming, range −32,768 to +32,767. Default integer type for counters, timer presets, and scaled analog values.

LINT means Long Integer — a 64-bit signed integer, range ±9.2 × 10¹⁸. Used for nanosecond timestamps and very large cumulative counters.

LREAL means Long Real — a 64-bit IEEE 754 double-precision floating-point data type with about 15-16 decimal digits of precision. Used when REAL's 7-digit precision is insufficient.

LWORD means Long Word — a 64-bit unsigned data type, range 0 to 18,446,744,073,709,551,615. Used for nanosecond-resolution timestamps and very large bit-packed registers.

Variable storing memory address of another variable for indirect addressing.

REAL means a 32-bit IEEE 754 single-precision floating-point data type with about 7 decimal digits of precision. Used for analog scaling, PID calculations, and engineering units that require fractions.

Data type capable of storing both positive and negative values.

SINT means Short Integer — an 8-bit signed integer in PLC programming, range −128 to +127. Used for small signed counts and Allen-Bradley boolean memory.

Variable-length character array for text data, typically with defined maximum length.

User-defined data type grouping different data types into single unit.

User-defined data type limiting variable to specific range of values.

Duration data type for timer values, typically in milliseconds.

Time within a day from 00:00:00 to 23:59:59.999.

Converting data from one type to another, like INT to REAL or DINT to INT.

UDINT means Unsigned Double Integer — a 32-bit unsigned integer, range 0 to 4,294,967,295. Used for IPv4 addresses, large positive counts, and millisecond timestamps.

UINT means Unsigned Integer — a 16-bit unsigned integer in PLC programming, range 0 to 65,535. The explicitly-unsigned counterpart to INT in IEC 61131-3.

64-bit unsigned long integer with maximum range for whole numbers.

Data type allowing same memory location to be accessed as different types.

Data type storing only positive values, doubling positive range.

USINT means Unsigned Short Integer — an 8-bit unsigned integer, range 0 to 255. The IEC 61131-3 explicitly-unsigned 8-bit type, equivalent to BYTE on most platforms.

WORD means a 16-bit unsigned data type in PLC programming, range 0 to 65,535. Used for Modbus holding registers, status words, and bit-packed flags (16 BOOLs in one variable).

Wide character string supporting Unicode for international character sets.