Graphics - Visual elements

Enhanced Definition

In the context of IBM mainframe systems and z/OS, "graphics" refers to the programmatic generation and display of visual information, often character-based, vector-based, or using specialized terminal capabilities, primarily for business data visualization, forms, and technical diagrams. Unlike modern high-resolution graphical user interfaces, mainframe graphics historically focused on efficient, text-terminal-compatible representations or specialized hardware output.

Key Characteristics

- Programmatic Generation: Graphics are typically generated by applications written in languages like COBOL, PL/I, or Assembler, using specific APIs (e.g., GDDM) to define visual elements.
- Terminal-Dependent: The capabilities and appearance of graphics are heavily influenced by the connected display device, ranging from character-based 3270 terminals with extended attributes to specialized graphics terminals or plotters.
- Character-Based and Vector-Based: Many "graphics" on 3270 terminals are achieved using extended character sets, block characters, and screen attributes. More advanced systems like GDDM support vector graphics for charts, graphs, and diagrams.
- Business and Technical Focus: Primarily used for displaying business charts (bar, pie, line graphs), technical diagrams, forms, and system monitoring dashboards rather than rich multimedia.
- Limited Resolution and Color: Compared to contemporary client-server or web interfaces, mainframe graphics generally feature lower resolution and a more restricted color palette.
- Server-Side Rendering: The graphical data is typically composed and rendered on the mainframe before being sent to the terminal for display or to a printer/plotter.

Use Cases

- Business Intelligence and Reporting: Generating and displaying charts and graphs (e.g., sales trends, financial performance, resource utilization) directly from mainframe data for operational insights.
- Interactive Forms and Data Entry: Creating visually structured forms with lines, boxes, and shaded areas on 3270 screens to guide users during data input in applications like CICS or IMS.
- System Monitoring and Operations: Visualizing system performance metrics, network topology, or storage utilization for system administrators through specialized console displays or applications.
- CAD/CAM and Engineering: Early computer-aided design and manufacturing applications utilized mainframe graphics capabilities for technical drawings and simulations.
- Plotting and Hardcopy Output: Producing high-quality hardcopy output of charts, diagrams, and technical drawings on specialized plotters connected to the mainframe.

Related Concepts

Mainframe graphics are intrinsically linked to GDDM (Graphical Data Display Manager), which is IBM's primary product for generating and managing graphical output on z/OS. They often interact with 3270 terminals and their extended attributes for character-based visuals, and applications running under CICS, IMS, or TSO can invoke GDDM services. The generated graphical data can be spooled via JES for printing or plotting, or displayed directly on compatible terminals, making it a component of the overall application presentation layer.

Best Practices:

Leverage GDDM: For new mainframe-native graphical development, utilize GDDM APIs for consistent and robust graphical output, as it provides a standardized interface across various display devices.
Optimize for Terminal Capabilities: Design graphics to gracefully degrade or adapt to the capabilities of the target terminal (e.g., monochrome vs. color, character-based vs. vector-capable) to ensure broad accessibility.
Minimize Data Transfer: When displaying graphics on remote terminals, optimize the graphical data stream to reduce network traffic and improve response times, especially for complex visuals.
Consider Modern Front-Ends: For new application development requiring rich, interactive graphics, it's often more efficient to use modern web or client-server front-ends that consume data from the mainframe via APIs (e.g., REST, MQ) and render graphics on the client side.
Provide Textual Alternatives: Ensure that any critical information conveyed graphically is also available in a textual or tabular format for accessibility, logging, and integration with other systems.