Incrementing a 2-Character Alphanumeric Code in RPG Free

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Incrementing a 2-Character Alphanumeric Code in RPG Free




Today I’m sharing a small but useful RPG Free program to increment a 2-character alphanumeric code using the sequence A..Z, 0..9. The program also handles wrap-around after "99", restarting at "AA".

Source Code

You can copy and paste the code directly from the field below:

How It Works

  • The program takes a 2-character input code.
  • It validates that both characters are within the allowed sequence A..Z,0..9.
  • It increments the second character and carries over to the first if necessary.
  • If the code exceeds "99", it wraps back to "AA".
  • If the input contains invalid characters, an error code INVALIDVAL is set and the output is cleared.

Ideas for Improvement

This simple module can be enhanced in several ways:

  • Handle codes longer than 2 characters.
  • Allow custom sequences, e.g., only letters or only numbers.
  • Create a reverse function to decrement a code.
  • Make the code case-insensitive.

Try it on your IBM i, experiment with improvements, and share your optimizations. Improving these small programs is a great way to become more skilled in RPG Free and DB2!

Comments

  1. AnonymousJanuary 20, 2026 at 3:32 AM

    here's my version. drawback: you cannot have a longer inputValue string than 2 chars
    personally, I would have prefer to build a function that returns the outputValue as a result instead of an additional parm. but, that's fine. Enjoy!

    **free
    Ctl-Opt DftActGrp(*No) ActGrp(*New) Option(*SrcStmt:*NoDebugIO);

    Dcl-PI RAAINCR;
    inputValue Char(2) Const;
    outputValue Char(2);
    errorCode Char(10);
    End-PI;

    Dcl-C Base36 36;
    Dcl-C ValidChars 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';

    Dcl-DS inputDS;
    chr1 Char(1);
    chr2 Char(1);
    End-DS;

    Dcl-S result Int(5);
    Dcl-S pos1 int(3);
    Dcl-S pos2 int(3);

    // Split inputValue chars
    inputDS = inputValue;

    // Validate inputValue
    pos1 = %Scan(chr1 :ValidChars);
    pos2 = %Scan(chr2 :ValidChars);
    If pos1 = 0 Or pos2 = 0;
    errorCode = 'INVALIDVAL';
    outputValue = *Blanks;
    Return;
    EndIf;

    // Increment inputValue. Beyond '99' restart from 'AA'
    result = %Rem(((pos1 - 1) * Base36 + (pos2 - 1) + 1) :Base36 * Base36);
    chr1 = %SubSt(ValidChars :%Div(result :Base36) + 1);
    chr2 = %SubSt(ValidChars :%Rem(result :Base36) + 1);

    // Build the resulting code
    outputValue = inputDS;

    Return;

    ReplyDelete

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