Function Package Table - IBM-REXX

The function package table contains information about the function packages that are available for the language processor environment.

An individual user or an installation can write external functions and subroutines. For faster access of a function or subroutine, you can group frequently used external functions and subroutines in function packages. A function package is a number of external functions and subroutines that are grouped together. Function packages are searched before load libraries and execs.

There are three types of function packages:

• User function packages
• Local function packages
• System function packages

User function packages are searched before local packages. Local function packages are searched before any system packages.

To provide a function package, there are several steps you must perform, including writing the code for the external function or subroutine, providing a function package directory for each function package, and defining the function package directory name in the function package table.

In the parameter block, the PACKTB field points to the function package table. The table contains information about the user, local, and system function packages that are available for the language processor environment. The function package table consists of two parts; the table header and table entries. Table 59 shows the format of the function package table header. The header contains the total number of user, local, and system packages, the number of user, local, and system packages that are used, and the length of each function package name, which is always 8. The header also contains three addresses that point to the first table entry for user, local, and system function packages.

The table entries specify the individual names of the function packages. The table entries are a series of eight-character fields that are contiguous. Each eight-character field contains the name of a function package, which is the name of a load module containing the directory for that function package. The function package directory specifies the individual external functions and subroutines that make up one function package.

illustrates the eight-character fields that contain the function package directory names for the three types of function packages (user, local, and system).

TSO/E provides a mapping macro for the function package table. The name of the mapping macro is IRXPACKT. The mapping macro is in SYS1.MACLIB.

Function Package Table Header

Function Package Table Entries – Function Package Directories

The table entries are a series of eight-character fields. Each field contains the name of a function package directory. The directory is a load module that, when loaded, contains information about each external function and subroutine in the function package.

The function package directory names in each eight-character field must be left justified and padded with blanks.