iX Computer Systems - Edition 1 (32715-90001)

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item and generates a SKIP. If adjacent items can be skipped, the Program

Analyst creates only one SKIP clause to cover those items. The items

that can be skipped are highlighted.

If skippable items are found, pressing RETURN will cause the Program

Analyst to create an ASCII file containing the following statements:

* The original PACKFMT line with the actual statement commented out

with a !.

* The new PACKFMT statement with a line number one greater than the

original.

When this file is merged (using the MERGE command) back into the program,

the original line serves as documentation of the complete record layout.

If you are referencing a PACKFMT statement by a line number instead of a

label, you need to modify the appropriate PACK or UNPACK statement.

When determining the number of bytes in a string variable, the Program

Analyst uses the maximum declared length (or 18 if the string is

undeclared). The Program Analyst assumes that strings are always padded

out to their maximum length before packing them. This is recommended

practice because the maximum length is always used during an UNPACK.

The Optimize PACKFMTs screen can also be used to optimize IN DATASET

statements. You can modify a IN DATASET statement so that it looks like

a PACKFMT statement, optimize the modified statement, merge the state-

ment

into the program, and then modify it back to an IN DATASET statement.

The Extract Subunit Screen. The purpose of this screen is to assist in

dividing large subunits into smaller subunits.

Manually removing lines form one part of a program and using the lines to

create a new subunit can be tedious. There are many dependencies that

must be examined. The Program Analyst can be very useful for extracting

subunits. Using the information in the interpreter, the Program Analyst

can detect all of the following dependencies:

* Branches that will be broken if lines are removed.

* Variables that have been shared between the old and new subunits that

must become parameters or placed in common.

* Single-line functions definitions and OPTION, IMAGE, and PACKFMT

statements that will be needed in the new subunit.

On entry of a line range, the Program Analyst displays the effects of

removing this line range from its subunit. The Program Analyst examines

all GOTOs, GOSUBs, and structured statements to determine whether they

would be affected. It also determines whether variables (including

files) need to be passed as parameters to the proposed new subunit. Once

you have identified a line range that can be extracted without breaking

any branches or structures, the Program Analyst creates the new subunit

and the CALL to it.