How IRXINIT Determines What Values to Use for the
Environment - IBM-REXX

When the system calls IRXINIT to automatically initialize a language processor environment, IRXINIT must first determine what values to use for the environment. IRXINIT uses the values that are defined in one of the three default parameters modules that TSO/E provides and the values that are defined for the previous language processor environment.

IRXINIT always identifies a previous language processor environment. If an environment has not been initialized in the address space, IRXINIT uses the values in the default parameters module IRXPARMS as the previous environment.The following topics describe how IRXINIT determines the values for a new environment when the system calls IRXINIT to automatically initialize an environment in the TSO/E and non-TSO/E address spaces.

Result:
If you call IRXINIT to initialize an environment, IRXINIT evaluates the parameters you pass on the call and the parameters defined for the previous environment.

Values IRXINIT Uses to Initialize Environments

When the system calls IRXINIT to automatically initialize an environment in the TSO/E address space, IRXINIT determines what values to use for defining the environment from two sources:

  • The default parameters module IRXTSPRM or IRXISPRM
  • The previous environment

During logon processing, IRXINIT initializes a language processor environment for the TSO/E session. IRXINIT first checks the values in the default parameters module IRXTSPRM. If the value is provided (that is, the value is not null), IRXINIT uses that value. If the value in the parameters module is null, IRXINIT uses the value from the previous environment. In this case, an environment does not exist, so IRXINIT uses the value from the IRXPARMS parameters module. IRXINIT computes each individual value using this method and then initializes the environment.

The following types of parameter values are considered to be null:

  • A character string is null if it contains only blanks or has a length of zero
  • An address is null if the address is 0 (or X'80000000', when specified for the user field parameter in the IRXINIT parameter list)
  • A binary number is null if it has the value X'80000000'
  • A bit setting is null if its corresponding mask is 0

For example, in IRXTSPRM, the PARSETOK field is null. When IRXINIT determines what value to use for PARSETOK, it finds a null field in IRXTSPRM. IRXINIT then checks the PARSETOK field in the previous environment. A previous environment does not exist, so IRXINIT takes the value from the IRXPARMS module. In this case, the PARSETOK field in IRXPARMS is null, which is the value that IRXINIT uses for the environment. If an exec running in the environment contains the PARSE SOURCE instruction, the last token that PARSE SOURCE returns is a question mark.

After IRXINIT determines all of the values, IRXINIT initializes the new environment.

When a user invokes ISPF from the TSO/E session, the system calls IRXINIT to initialize a new language processor environment for ISPF. IRXINIT first checks the values provided in the IRXISPRM parameters module. If a particular parameter has a null value, IRXINIT uses the value from the previous environment.In this case, the previous environment is the environment that IRXINIT initialized for the TSO/E session. For example, in the IRXISPRM parameters module, the mask bit (CMDSOFL_MASK) for the command search order flag (CMDSOFL) is 0. A mask of 0 indicates that the corresponding flag bit is null.Therefore, IRXINIT uses the flag setting from the previous environment, which in this case is 0.

As the previous descriptions show, the parameters defined in all three parameters modules can have an effect on any language processor environment that is initialized in the address space.

When IRXINIT automatically initializes a language processor environment in a non-TSO/E address space, IRXINIT uses the values in the parameters module IRXPARMS only.

If you call the IRXINIT routine to initialize a language processor environment, you can pass parameters on the call that define the values for the environment.

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