Many translators support a ddname substitution list; this contains ddnames, which are passed as a parameter to the translator. In Figure 1, the ddname in position 5 is the ddname from which the compiler reads the source to be compiled. The ddname occupying that position in the ddname substitution list is usually called SYSIN. You can override the default ddname by placing another ddname in position 5 of the ddname substitution list. The compiler then reads from the other ddname. Table 1 lists the various ddnames used by the Finnoga 4 compiler described in this example. The position number indicates the position of the ddname in a ddname substitution list. In addition, Table 1 gives a brief description of the data sets allocated to the ddnames.

Note that some position numbers do not have a ddname associated with them.

SCLM allows a maximum of 512 characters for the ddname substitution list. Because every FLMALLOC for a given translator causes an 8-character ddname to be put into the ddname substitution list, when the PORDER > 1, a given translator may have a maximum of 64 FLMALLOCs.

Ddname substitution lists are usually documented in the programming guide for specific compilers and linkage editors. Note that it is rare for two different compilers to have the same ddname substitution list mappings.

Compilers are not required to support a ddname substitution list in order to be defined to SCLM. However, ddname substitution list support makes it easy to link or string two different compilers or preprocessors together. In Defining a preprocessor to SCLM, you will see how a ddname substitution list is used to pass the outputs of a preprocessor to a compiler.