IBM Common User Access

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Common User Access (CUA) is a set of guidelines for the user interface to operating systems and computer programs, developed by IBM and first published in 1987 as part of their Systems Application Architecture. Used originally in the OS/MVS, VM/CMS, OS/400, OS/2 and Microsoft Windows operating systems, parts of the CUA standard are now implemented in programs for other operating systems, including variants of Unix. It is also used by Java AWT and Swing, and can be enabled in GNU Emacs.

The CUA contains standards for the operation of elements such as dialog boxes, menus and keyboard shortcuts that have become so influential that they are implemented today by many programmers who have never read the CUA.

Some of these standards can be seen in the operation of Windows itself and DOS-based applications like the MS-DOS 5 full-screen text editor EDIT. CUA hallmarks include:

• All operations could be done with either the mouse or the keyboard;
• Menus are activated/deactivated with the F10;
• Menus opened by pressing the Alt key plus the underlined letter of the menu name;
• Menu commands which require parameters to proceed are suffixed with an ellipsis ("...");
• Options are requested using dialog boxes;
• Navigation within fields in dialog boxes is by cursor key; navigation between fields is by pressing [Tab] or [Shift]+[Tab] to go backwards;
• Dialog boxes should have a 'Cancel' button activated by pressing the [Esc] key which discards changes and an 'OK' button activated by pressing [Return] which accepts changes;
• The program should have 'online help' with a Help menu as the last option on the menu bar; context sensitive help can be summoned by [F1];
• The first menu should be called "File" and contain operations for handling files (new, open, save, save as) as well as quitting the program; the next menu 'Edit' has commands for undo, redo, cut, copy, delete, paste commands;
• The Cut command is [Shift]+[Del]; Copy is [Ctrl]+[Ins]; Paste is [Shift]+[Ins];
• The size of a window can be changed by dragging one of the 8 segments of the border.

CUA was a detailed specification and set strict rules about how applications should look and function. Its aim was in part to bring about harmony between MS-DOS applications, which until then had implemented totally different user interfaces.

Examples:

• In WordPerfect, the command to open a file was [F7], [3].
• In Lotus 1-2-3, a file was opened with [/] (to open the menus), [W] (for Workspace), [R] (for Retrieve).
• In Microsoft Word, a file was opened with [Esc] (to open the menus), [T] (for Transfer), [L] (for Load).
• In WordStar, it was [Ctrl]+[K]+[O].
• In emacs, a file was opened with [Ctrl]+[x] followed by [Ctrl]+[f] (for find-file).

Some programs used [Esc] to cancel an action, some used it to complete one; WordPerfect used it to repeat a character. Some programs used [End] to go to the end of a line, some used it to complete filling in a form. [F1] was often help but in WordPerfect that was [F3]. [Ins] sometimes toggled between overtype and inserting characters, but some programs used it for "paste".

Thus, every program had to be learned individually and its complete user interface memorized. It was a sign of expertise to have learned the UIs of dozens of applications, since a novice user facing a new program would find their existing knowledge of a similar application absolutely no use whatsoever.

This detailed specification drew some of its inspiration from Apple Computer's lavishly detailed Human Interface Guidelines. The Apple HIG is a detailed book specifying exactly how software for the Apple Macintosh computer should look and function. When it was first written, the Mac was new and GUI software was a novelty, so Apple took great pains to ensure that programs would conform to a single shared look and feel. CUA had a similar aim, but faced the more difficult task of trying to impose this retroactively on an existing, thriving but chaotic industry.

However, CUA did not only cover DOS applications; it was also the standard on which the Windows CUI ('consistent user interface') was designed, as well as that for OS/2 applications - both text-mode and the Presentation Manager GUI - and IBM mainframes which conformed to the Systems Application Architecture. Thus CUA was more than just an attempt to rationalise DOS applications - it was part of a larger scheme to bring together, rationalise and harmonise the overall functions of software and hardware across IBM's entire computing range from microcomputers to mainframes. As this encompassed PCs and compatibles, it extended to the PC industry - which is perhaps part of the reason it was not completely successful.

The third edition of CUA took a radical departure from the first two by introducing the object-oriented workplace. This changed the emphasis of the users interactions to be the data (documents, pictures, and so on) that the user worked on. The emphasis on applications was removed with the intention of making it much easier to use than other systems.

The workplace was adopted by Microsoft in the 1995 version of Windows. Critically the Start menu was introduced which removed the emphasis on an object oriented desktop.

[edit] References

• IBM, Systems Application Architecture: Common User Access: Panel Design and User Interaction, Document SC26-4351-0, 1987.
• IBM, Systems Application Architecture: Common User Access: Advanced Interface Design Guide, Document SC26-4582-0, 1990.
• IBM, Systems Application Architecture: Common User Access: Basic Interface Design Guide, Document SC26-4583-0, 1990.
• IBM, Systems Application Architecture: Common User Access: Guide to User Interface Design, Document SC34-4289-00 1991
• IBM, Systems Application Architecture: Common User Access: Advanced Interface Design Reference, Document SC34-4290-00 1991