Keyword Descriptors

Keyword descriptors, introduced in the previous section, add the final refinement to the level 1 keyword. These descriptors can be characters (c), integer numbers (i), or real numbers (r), depending on the entry format. A real number possesses a decimal point, such as “3.0”. An integer does not have a decimal point, such as “3”.

All numerical data is assumed to utilize MKSA units. Data are entered with a maximum length of 128 characters per record. For records containing numerical descriptors only (no character descriptors), blank spaces, commas, or tabs can be used as delimiters.

It is important to realize that a descriptor entry takes on a different meaning depending upon the alphanumeric type (c, i, r) used. For instance, the following data entries are perfectly legal.

The first line of either entry group is the keyword, “SPACE STEP”. The second line consists of keyword descriptors. In the first entry there are two keyword descriptors. These are:

segment1 25.0

In the second entry, there are also two keyword descriptors. These are:

segment1 25

Upon first inspection, these keyword descriptor lines may appear identical, or at least equivalent. However, the second descriptor of the first entry is a real number, “25.0”, and the associated descriptor of the second entry is an integer, “25”. The different datum types imply two totally different meanings. In the first entry the real number defines the finite difference space step of segment1 to be 25.0 meters. In the second entry, the integer defines the number of finite difference increments assigned to segment1. If segment1 is 25.0 meters long, then the finite difference space step would be 1.0 meters in length. It is thus of paramount importance that a real number be entered with a decimal point, or in scientific notation, and there be no decimal point associated with an integer.