Skip to main content

Advantage of Using Sub-Procedures over Sub-routines in RPGLE

Need for Sub-Procedures or Sub-Routines:

The main advantage of using subroutines is intellectual manageability. That is, I can think of a program as a group of related small tasks, all of which are simple enough for me to understand, rather than as one gargantuan task that is more than I can handle. This gives ease in modifying/bug fixing of a program.

Debugging seems to be easier because I can often determine which subroutine most likely contains an error. Finding a logic error in a program of sub-procedures/sub-routines is easier when compared against the program which has complete logic in single routine.

Sub-Procedures/Sub-Routines also promotes the re-usability of code.

Limitations of Sub-Routines:

1.     Sub-Routines use global variables only.

That is, any variable or constant or indicator that I use in a subroutine may be used anywhere else in the program--in the main calculations, in any subroutine, in output specs. This can lead to undesirable side effects. Changing the value of a variable in one part of the program causes something to go wrong in another part of a program.

So, copying the code of sub-routine to different program would need changes to be done in view of variables.

2.     Inability to use Parameters.

If we have a code that performs specific calculation based on input parameters, we would need to initialize the variables before calling the program.

Advantages of Sub-Procedures:

1.     Sub-Procedures allow you to define local variables.

Local variables would be allowed only inside sub-procedure. So, there is no risk by using the variables with same name in other sub-procedures or main line. These variables cannot be referenced outside of the program.

2.     Ability to use parameters.

Parameters make sub-procedures more portable by providing internal names for required data. It makes program maintenance easy when the procedure is being called from multiple routines.

3.     Returning a Value

Sub-procedure has the ability to return a value. It can be used as how BIF are being used on operations like EVAL, IF etc.

4.     Ability to use Sub-Procedure across application.

If we have Sub-Procedure that will be useful across application, It can be attached to Service Program and made available to access across application.


Popular posts from this blog

All about READ in RPGLE & Why we use it with SETLL/SETGT?

READ READ is one of the most used Opcodes in RPGLE. As the name suggests main purpose of this Opcode is to read a record from Database file. What are the different READ Opcodes? To list, Below are the five Opcodes.  READ - Read a Record READC - Read Next Changed Record READE - Read Equal Key Record READP - Read Prior Record READPE - Read Prior Equal Record We will see more about each of these later in this article. Before that, We will see a bit about SETLL/SETGT .  SETLL (Set Lower Limit) SETLL accepts Key Fields or Relative Record Number (RRN) as Search Arguments and positions the file at the Corresponding Record (or Next Record if exact match isn't found).  SETGT (Set Greater Than) SETGT accepts Key Fields or Relative Record Number (RRN) as Search Arguments and positions the file at the Next Record (Greater Than the Key value). Syntax: SETLL SEARCH-ARGUMENTS/KEYFIELDS FILENAME SETGT  SEARCH-ARGUMENTS/KEYFIELDS FILENAME One of the below can be passed as Search Arguments. Key Fiel

What we need to know about CHAIN (RPGLE) & How is it different from READ?

CHAIN READ & CHAIN, These are one of the most used (& useful) Opcodes by any RPG developer. These Opcodes are used to read a record from file. So, What's the difference between CHAIN & READ?   CHAIN operation retrieves a record based on the Key specified. It's more like Retrieving Random record from a Database file based on the Key fields.  READ operation reads the record currently pointed to from a Database file. There are multiple Opcodes that start with READ and all are used to read a record but with slight difference. We will see more about different Opcodes and How they are different from each other (and CHAIN) in another article. Few differences to note.  CHAIN requires Key fields to read a record where as READ would read the record currently pointed to (SETLL or SETGT are used to point a Record).  If there are multiple records with the same Key data, CHAIN would return the same record every time. READE can be used to read all the records with the specified Ke

Extract a portion of a Date/Time/Timestamp in RPGLE - IBM i

%SUBDT Extracting Year, Month, Day, Hour, Minutes, Seconds or Milli seconds of a given Date/Time/Timestamp is required most of the times.  This can be extracted easily by using %SUBDT. BIF name looks more similar to %SUBST which is used to extract a portion of string by passing from and two positions of the original string. Instead, We would need to pass a value (i.e., Date, Time or Timestamp ) and Unit (i.e., *YEARS, *MONTHS, *DAYS, *HOURS, *MINUTES, *SECONDS or *MSECONDS) to %SUBDT.  Valid unit should be passed for the type of the value passed. Below are the valid values for each type. Date - *DAYS, *MONTHS, *YEARS Time - *HOURS, *MINUTES, *SECONDS Timestamp - *DAYS, *MONTHS, *YEARS, *HOURS, *MINUTES, *SECONDS, *MSECONDS Syntax: %SUBDT(value : unit { : digits { : decpos} }) Value and Unit are the mandatory arguments.  Digits and Decimal positions are optional and can only be used with *SECONDS for Timestamp. We can either pass the full form for the unit or use the short form. Below i