During the execution of the program, the value of the pointer variable is set to the location address in storage of the variable LINE by means of the ADDR built-in function. The following sections cover these topics: Data types used with based variables: pointers, areas, and offsets Allocation in areas Mechanisms for referring to based variables and for obtaining pointer values to them Based variables and dynamic storage allocation The ADDR built-in function Data type matching for based variables Examples of based variables in use, including allocation in areas 5.
A pointer is a variable whose value represents the location in memory of another variable or data item. Areas are regions of storage in which based variables can be allocated and freed. The use of areas can simplify and speed operations involving large or numerous based variables. An offset is a value indicating the location of a based variable relative to the beginning of an area. If you use the ALLOCATE statement with an area either implied or explicitly specified , you can cause the allocation of storage to be performed in that area, instead of in the general memory pool for based and controlled storage.
Storage management in areas has a number of uses, including the following: To allow an area to be moved to different addresses without invalidating its data.
To allocate storage that can be freed all at once with low overhead, by allocating variables in an area and then emptying the areas with the EMPTY built-in function rather than freeing the generations one at a time. To allocate storage that can be rolled back, by allocating variables in an area and making periodic assignment of the area to a backup area. If it is found that some operations need to be rolled back, the backup area can then be copied back into the current area or they can be swapped.
Note that when areas are assigned to each other, all offsets into the old area are valid for the new area as well. To use areas to overlay shared memory sections, which can be mapped into different address ranges in different processes.
This mechanism is intended only as a debugging aid. The SET option itself can be implied from the base variable. Whether an area is specified explicitly or implied, the allocation is performed in that area instead of in the available memory pool for based and controlled storage. If an error is detected in the process, the AREA condition is raised.
These extensions are as follows: Area control information is stored in the form of offsets so that an area can be moved to different addresses and still be correct see Section 3. As a result, you can assign areas as members of structures as long as their extents are identical.
The macros have the same name as the control blocks and have the. They describe the key problem program state fields. Only fields that are supported are named in the macros; the others are defined as "fillers". On the mainframe, the PSA can be addressed directly. To avoid this, you should use the idalpsa macro to locate the PSA. This macro sets a given pointer to the address of the PSA.
The idalpsa macro is contained in the idalpsa. For each project, a readme. The chapter Compiling and Linking Assembler Modules in the Assembler Option Technical Guide provides a full description of how modules can be linked together, including the difference between static linking which takes place at build time and dynamic linking which takes place at run time. You can run the utility in batch or interactive mode.
If you specify a file that already exists, you will be given the choice of appending to it or replacing it when you click Generate later. If you specify a field prefix and want to use the actual field names instead of numbers for the variable part of each name, select the Text radio button.
Then, for example, the fields in the above structure could be generated as:. Do not assign a prefix containing characters that are not supported by the compiler or that make the field name too long. These are direct addressing and indirect addressing. The PCB address list format applies only to main programs.
The second field is available only when indirect addressing is specified for the first. This exit is controlled by the EXIT compiler directive and is set on by default. All rights reserved. This document and the proprietary marks and names used herein are protected by international law. Filenames containing spaces are not supported.
You should use the. For more information see the section Mixed-language Applications later in this chapter. On the PC, no dummy records are added beyond the record written with the highest key. The Linker page is shared with Assembler Option.
If some modules use bit addressing, you need to specify this individually on the Build Settings dialog box.
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