Screen Design Aid

Screen Design Aid (System/34 and System/36)

SDA is a utility for the IBM System/34, System/36, System/38, and AS/400 (iSeries) midrange computers.

This article refers to the S/34 and S/36 implementations of SDA. S/38 and AS/400 use a different SDA with different syntax and characteristics. See the AS/400 article for more about these midrange computers.

SDA stands for Screen Design Aid. Programmers can use SDA to create menus, display formats, or WSU skeleton programs.

IBM midrange computers utilize display stations to present information and to accept information and control from computer operators. A display station is an input/output device comprised of a monitor and a keyboard.

S/34 and S/36 applications usually involve the operator to a critical degree, whether accepting the bulk of input through display stations or controlling them. Computer programs may utilize unformatted or formatted input, and this is where SDA applies.

Starting SDA

From any menu, type SDA and press Enter.

Using SDA To Design A Menu

Option 1 from SDA is to design a menu. Two different displays are used. On the first display, build the menu by typing the displayed menu text. The System/34 convention describes fixed-format and free-format menus. In a fixed-format menu, describe each menu item in 30 characters or less. In a free-format menu, lay out your menu exactly as you want it to appear. Press Cmd9 when you are done.

On the second display, type the commands, procedures, or OCL associated with each menu item you are using. Many S/3X programmers use option 24 for sign-off, but this is not required. Press Cmd9 when you are done.

When you have completed these displays, SDA is ready to build your menu for you. Select your print and compile options and press Enter.

Creating Display Formats or Menus From Code

Like RPG II, display formats are built from column-sensitive specifications which describe fields of fixed sizes with fixed or conditioned properties.

All display formats have exactly one coded S specification, which describes the size of the format, the keys which may be used, the lines to be cleared, special functions such as sounding the Alarm (the "raspberry" sound is the only sound a S/3X terminal can be programmed to make), and most importantly the name of the format which must be referenced by the HLL (High-Level Language) program.

Display formats may have one, many, or no D ("Detail") specifications to describe the field(s) used in the display. These fields may be constants, input, output, or input-output. Properties such as Nondisplay and Protected may seem to defeat the purpose of having the field, but there are non-intuitive uses for these fields.

Display formats are so attuned to the RPG II language as to require language extensions when used with other HLLs. The 99 numbered RPG indicators perfectly match the screen indicators; however, take caution when coding display formats that you reserve indicator usage to match the current conditioning of the indicator when the display is written - otherwise, a dummy indicator used for Half-Adjust may end up positioning the cursor incorrectly.

Accessing SDA Displays From S/3X Programs

In RPG II, use the WORKSTN device.

In COBOL, use the CONSOLE device.

In BASIC, OPEN a filespec and describe it as WORKSTN.

In OCL, use the PROMPT statement.

Coding For Your Audience

When the IBM System/34 was sold, a common monitor would be a monochrome 12-inch IBM 5251; in the System/36 heyday, a common monitor would be the 12-inch IBM 5291 or the color 14-inch IBM 3486. Later in the S/36 life, third parties began to rise in popularity with such names as IIS, Decision Data, and Emerald. Not only do the third-party monitors cost much less, they offer multiple session capability, programmable color palettes, larger display areas, and a direct PC printer port which allows S/36 users to access inexpensive inkjet printers without a separate adapter. This is one reason why programming the S/36 has become more interesting over the years - the "blue" or "red" field you code may not appear blue or red on all audience equipment.

All S/34 and S/36 display stations use 5250 protocol; S/34 allows either 960-character displays or 1920-character displays; S/36 allows either 1920-character displays or (rare) 3564-character displays.

Code two different display formats if it is possible that your audience might use the IBM 5252 Dual Display, which requires 960-character displays. Consider whether your audience will be using color or monochrome displays - an application developed for color-only might not function well on a monochrome display.