DLT(ID:4688/ibm002)Decision table generatorIBM 1401 Decision Logic Translator IBM Application Program, #H20-0068-0, pg 1 Structures: References: Decision Logic Translator The IBM 1401 Decision Table Logic Translator program "was designed to ease the burden placed upon those who are responsible for implementing an Automated Design Engineering System."* The program is actually a preprocessor in which the logic of the decision tables is translated into a FORTRAN source program. Some permitted operators in the condition portion are the typical FORTRAN GE (greater than or equal to), GR (greater than), EQ (equal), NE (not equal), LR (less than), LE (less than or equal to). In the action area, the following special verbs are used in addition to the normal FORTRAN verbs: SET (set operand 1 equal to operand 2), INCREMENT (increment operand. I by operand 2), DO FORMULA, DO TABLE, ERROR (to go to a specified table in case there is an error in input), GO TO TABLE, RETURN (to return control from a closed table to the referencing table). These words, along with some other words (READ, PA USE, etc.) which have the common FORTRAN interpretation, are called keyiuords. This preprocessor accepts both limited and extended entry rows. Extended entry rows will usually" appear at the top of the table after sorting. When a limited entry table is sorted, the condition rows with the fewest blank entries will appear first; then the rules are sorted in a manner similar to that described in Chapter Seven. The sorting procedure enables the preprocessor to produce a more efficient condition testing procedure. Only one set of // statements may be generated if a scan of the condition entries detects identical groups of conditions within two or more columns. Condition and action rows of the original table are listed and validity checked. One or more FORTRAN statements are generated for each of the actions to be executed. If a formula is referenced more than once, it is coded out of line. Else rules are permitted, and closed tables may reference other closed tables. One of the significant restrictions and requirements is that all variable and constant names must follow FORTRAN specifications. Also, there may be no more than forty rules per table, and the minimum combined number of condition and action rows must be less than one hundred. If the table contains extended entry rows, the total number of actions and conditions must be less than one hundred after the extended entry rows are converted to the limited entry format. Other than the input listing, a FORTRAN II source program listing is produced with diagnostics, where pertinent, and the generated FORTRAN II source program deck is punched. After the deck is punched, the user must insert the correct FORMAT information into a FORMAT card. This translator, while excellent in many respects, cannot check the table for completeness, redundancy, or inconsistency. This deficiency arises mainly because of the way the else rule is used in the table inputs. While the else rule may shorten the time required to write a table, the machine and debugging times may be lengthened. Also, the method used to develop testing sequence may result in many unnecessary test instructions. |