Built-in Functions in RPGLE

Learning Objective

By the end of this lesson, you will understand what a built-in function is in RPGLE, and be able to use a few of the most common ones: %TRIM, %LEN, %SUBST, %CHAR, and %DEC.

Simple Explanation

In the Expressions and Assignment in RPGLE lesson, you learned how to combine variables, literals, and operators into expressions. RPGLE also provides built-in functions, sometimes called BIFs, which are ready-made operations you can use inside an expression, always written starting with a percent sign (%).

A few especially common built-in functions include:

• %TRIM(value): removes extra blank spaces from the beginning and end of a character value.
• %LEN(value): returns how many characters long a value currently is.
• %SUBST(value : start : length): pulls out a portion of a character value, starting at position start, for length characters.
• %CHAR(value): converts a numeric value into its character (text) representation.
• %DEC(value : totalDigits : decimalDigits): converts a character value into a packed decimal number with the specified total digits and decimal digits.

dcl-s rawName char(30);
dcl-s trimmedName char(30);
dcl-s nameLength int(10);
dcl-s firstThree char(3);

rawName = 'Jordan Lee                   ';
trimmedName = %trim(rawName);
nameLength = %len(trimmedName);
firstThree = %subst(trimmedName : 1 : 3);

Why It Matters

Built-in functions handle small, common tasks, cleaning up text, converting between data types, pulling out part of a value, that would otherwise require writing extra logic by hand every time. Recognizing a handful of frequently used ones, especially %TRIM, %LEN, %SUBST, %CHAR, and %DEC, covers a large share of what you will actually reach for in everyday RPGLE code.

Practical Example

Imagine a program that receives a customer name with extra trailing spaces, perhaps from an external system. Before displaying or comparing that name, the program uses %trim to remove the extra spaces, ensuring the value is clean and predictable to work with, rather than accidentally including blank padding when the name is used elsewhere in the program.

This is a simplified, illustrative example rather than a specific real integration, but it reflects a very common, everyday reason %TRIM specifically is one of the most frequently used RPGLE built-in functions.

Common Confusions

"Is a built-in function the same thing as a procedure I write myself?" Not quite. Built-in functions are provided directly by the RPGLE language itself, always starting with %, and are ready to use without any declaration. Procedures, covered in a later lesson, are blocks of logic you define yourself.

"Why do %SUBST and %DEC use colons between their arguments?" The colon separates multiple pieces of information a built-in function needs, such as %SUBST(value : start : length) needing the value, a starting position, and a length. This is simply RPGLE's syntax for built-in functions that take more than one piece of information.

"Does %CHAR always produce a fixed-length result?" No. %CHAR produces a character value only as long as it needs to be to represent the number, without extra padding, which is worth keeping in mind if you plan to combine or compare its result with other character values.

Quick Recap

• Built-in functions (BIFs) are ready-made RPGLE operations, always written starting with %.
• %TRIM removes extra blank spaces; %LEN returns a value's current length; %SUBST pulls out part of a character value.
• %CHAR converts a number to character data; %DEC converts character data to a packed decimal number.
• Built-in functions handle common, everyday tasks without needing to write extra logic by hand.

Try Asking the AI Tutor

Use the AI Tutor to ask follow-up questions about this lesson. For example, try asking:

• "What are some other commonly used RPGLE built-in functions besides %TRIM, %LEN, %SUBST, %CHAR, and %DEC?"
• "What happens if %SUBST tries to pull out more characters than the value actually has?"