The Program Tab (PT) order advances the current buffer address and optionally clears the buffer. This works well for clearing a field of its contents on an already formatted screen without transferring a large amount of data in the data stream. This is especially true for scroll areas where only a partial view is valid.
CA Gen runtime uses a PT order to clear fields when the result should be a blank field. If other data replaces the field, use a PT order at the end of the new data to clear the remainder of the field.
Consider the example of a field defined as 40 bytes in length. It currently contains a 32 byte string, which will be replaced by an eight byte string. The PT order can be appended to the eight-byte string in the data stream to clear the remainder of the existing field. In this mode, the PT order acts like a user placing the cursor in a field and pressing the Erase/EOF key. The current buffer address is advanced to the next field. The runtime requires a Set Buffer Address (SBA) order to move the current buffer address.
When the PT order is suppressed, the runtime software sends the entire string, padded with spaces or Nulls, to clear fields.
To suppress the PT order, modify the Screen Table in the generated screen manager program.
Suppressing this feature makes it possible to use non-IBM 3270 systems that do not support this order.
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