Frames
A frame is a control structure for the sequencing of events within a process. Each process consists of one or more frames, executed according to their relative sequence number.
Each frame defines a specific activity, or set of actions, that are performed as part of a process. These actions include such things as the display of information to a user, retrieval of information from a user, execution of procedural code, and the invocation of other processes. For example, a single input process may require several screens to enter all of the necessary data, each of which represents a separate frame in the process.
If a process has a related process control file (PCF), the sequence of frames is executed once for each PCF record that is processed. For example, a transaction report program, with a transaction file PCF, executes its frame sequence once for every record in the transaction file. If the process does not have a PCF, the sequences of frames executes once, and the process ends.
The frame chronology is modified slightly for the following types of frames:
An optional frame,containing an image that conditionally displays based upon the value in the predefined field ALTERNATE IMAGE NUMBER. APPX does not display the image for an optional frame if the value is 0.
A repeating frame,containing an image that continues to display repeatedly until the value in the ALTERNATE IMAGE NUMBER predefined field is 0.
A scrolling frame, which is a type of input or output frame that displays more than a single image (one for each record, up to a maximum number of images) and formats those images into rows and columns. Refer to The Effect of Scrolling Frames on Screen and Page Positioning section for a detailed discussion of scrolling frames.
The functions of a frame vary slightly from one process type to another. In general, a frame:
Sequences multiple activities (including the invocation of automatic child processes), which occur within the confines of a single process.
Defines a region of the screen or printed output that images can display on.
Groups alternate images.
The frame itself incorporates both the image component of a process and a subset of the process event points. In addition, each frame may invoke one or more automatic child processes. |