Display Control Device for Legacy COBOL Multi-Screen Support
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Solution Overview
Problem
Legacy COBOL applications that use a sequential process for screen input and output, such as file OPEN, WRITE, and CLOSE commands, cannot display multiple screens simultaneously without significant modification, which is costly and limits multi-device support.
Innovation Solution
A display control method that creates and stores setting information for multiple screens in memory, allowing simultaneous display by treating one screen as the input target for drawing data transmission, enabling multiple screens to be displayed on a terminal device using existing applications without modification, and supporting multi-device environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If COBOL applications use sequential process for screen input and output, then the application structure remains simple and maintenance is easier, but multiple screens cannot be displayed simultaneously
Solution Approach 1:
A screen management table is introduced as an intermediary data structure to manage multiple screen settings. The table stores screen identification, input target flags, and other parameters for each screen. This intermediary layer allows the sequential COBOL application to indirectly control multiple screens without modifying the application's core sequential logic, thus enabling multi-screen display while maintaining application simplicity
Solution Approach 2:
The screen management system is designed with universal functionality to handle various screen operations through a unified interface. The same sequential process can request display of different screens by setting appropriate parameters in the screen management table, making the system adaptable to multiple screen scenarios without requiring application-specific modifications for each screen
2Adaptability or versatility
If COBOL applications are modified to support multiple screens, then multi-device support is enabled, but the cost of modification increases significantly
Solution Approach 1:
The screen management functionality is extracted from the COBOL application itself and implemented as a separate display control device. The application only needs to issue simple display requests without embedded screen management logic. This extraction eliminates the need for costly application modifications while enabling multi-device support, as the complex screen management is handled externally by the display control device
Solution Approach 2:
The system is segmented into two independent parts: the legacy COBOL application and the display control device. The application handles business logic while the display control device handles screen management. This segmentation allows the application to remain unchanged and simple, while the display control device provides advanced multi-screen and multi-device capabilities
3Ease of operation
If only one screen is treated as input target at a time, then input focus management is simplified, but user interaction with multiple screens is limited
Solution Approach 1:
The input target screen is dynamically determined based on the timing of display requests relative to the sequential process execution. When a display request is received during process execution, that screen becomes the input target. This dynamic assignment allows the system to manage input focus automatically without complex user intervention, while still enabling interaction with multiple screens as the input target can change over time
Data Source
AI summary
A display control method executed by a computer, the method includes creating information that indicates settings for a new screen and storing the created information in a memory, in response to receiving a drawing request to cause a terminal device to draw the new screen, from an application that controls input and output of a screen by a sequential process that executes processes in a predetermined processing order; treating the new screen as the input target screen and transmitting drawing data to draw the new screen to the terminal device, based on the information for the new screen; and treating the new screen among screens as the input target screen and transmitting drawing data to draw the screens collectively, to the terminal device, based on information for each of the screens, when the information for the screens is stored in the memory.