Extended Graphic Character Set (EGCS)

Extended Graphic Character Sets (EGCS) extend the number of graphic characters beyond the limit available using EBCDIC. This is an extension of the programmed symbol feature. The programmed symbol is an optional feature on the IBM® 3270 Information Display Station and SCS1 printers that store and use the additional character sets.

Where DBCS or DBCS/EBCDIC mixed fields are discussed in context with 3270 displays or SCS1 printer devices, it is assumed that these devices are capable of handling DBCS data. Such devices include, for example, the 5550, supported as a 3270 display, and the 5553 and 5557, supported as SCS1 printers.

Definition: The Double Byte Character Set (DBCS) is a subset of EGCS. In it, each graphic character is represented by 2 bytes. The valid code range is X'4040' or X'41' through X'FE' for byte 1, and X'41' through X'FE' for byte 2.

An EGCS field is defined by the EATTR= parameter on the DFLD statement for 3270 displays or SCS1 device types.

All EGCS literals are in the form G'SO XX .... XX SI', where SO (shift out)=X'0E' and SI (shift in)=X'0F'.

For SCS1 device types, EGCS is specified as a pair of control characters framing the data in the form of: G'SO XX XX XX SI'. The framing characters SO (shift out) and SI (shift in) are not actual characters, but are 1-byte codes: X'0E' or X'0F'.

EGCS literals must be specified as an even number of characters; otherwise, a warning message is issued. All characters (X'00' through X'FF') are valid in an EGCS literal; however, a warning message is issued for all characters not within the range of defined graphics, X'40' through X'FE'.

Restriction: An EGCS literal cannot be equated using the EQU statement if a hexadecimal value within the literal is an X'7D', which is equivalent to a quote character.

For the MFS Language utility to recognize an EGCS literal, observe the following restrictions when defining the EGCS literal:

An EGCS literal can be continued on the next line. An SI character can be coded in column 70, 71, or 72 to terminate EGCS data and is not included in the literal. If an SI is in column 70, the data in column 71 is ignored, except when it is a single quotation mark. On continuation lines for literals, an SO character is not required but can be used, if it is placed in column 15. (This indicates the beginning of EGCS data and is not included in the literal).

Restriction: IMS does not support a 2-byte fill function, inbound or outbound. For outbound data, the MFS fill function is at the message level. To avoid MFS insertion of RA (Repeat to Address) orders for EGCS fields that contain no data or are omitted in the output message, FILL=PT (the default) or FILL=NULL must be specified.

The MFS Language utility uses SO and SI characters in its output listing only for the initial input statement and for error messages that display EGCS literals from the input record. EGCS literals that are a part of the device image map are displayed as a series of Gs. Additional utility output that is created by using the EXEC PARM= operands DIAGNOSTIC, COMPOSITE, and SUBSTITUTE, and that contains EGCS literals, does not have the G, SO, and SI characters inserted. Only the data between the SO and SI characters is included.

You must define the screen location (row and column) where the field is to be displayed. This includes any screen placement constraints imposed by a particular product implementation. Warning messages are issued when:

When defining an EGCS field for a 3283 Model 52, you must ensure that the length specified is an even number and, if an EGCS field spans device lines, specify WIDTH= and POS= so that an even number of print positions are reserved on each of the device lines.