Keywords

All the parameters a program needs to fulfill its purpose, other than the raw (e.g. image, table) data and their descriptors, are called keywords  in MIDAS. The keywords are implemented as a global data structure in the environment and thus provide communication among different (main) programs. Keywords consist of a name, a type and a number (max. 32767) of associated data values of the given type. The keyword name  is a character string of maximum 8 alpha-numeric characters (case insensitive) starting with a letter. The keyword type  is either `Integer', `Real', `Double Precision', or `Character',     for INTEGER, REAL, DOUBLE PRECISION, CHARACTER (in FORTRAN 77) or int, float, double, char (in C). They fall into 4 distinctive groups:

a) MIDAS reserved keywords .

These keywords are used by MIDAS system programs and are generally of no concern to the application programmer. Great care should be taken when modifying these keywords!

b) Fixed keywords .

These keywords are fixed in their meaning, size and data type in order to obtain some standardization (otherwise one might end up having many different keywords describing the same parameter). Application programs may read and write these keywords.

c) User-defined keywords .

These keywords are used by application programs to define and handle parameters not covered by the fixed keywords. Application programs may define, delete, read and write user-defined keywords as needed for their purposes.

d) Local keywords .

These keywords are used like local variables in MIDAS procedures. Local keywords are only known within the context of the particular procedure where they are defined (and optionally in the procedures called from it). In case of doubly defined names, the local keyword takes precedence. Application programs cannot tell a local from a global keyword .