Program Logic Manual - All about the IBM 1130 Computing System

If at any time during the compilation an entrycannot be made to the statement string or the SymbolTable due to the lack of sufficient storage, an overlaperror condition exists. In the event of such an overlapcondition, the remaining compilation is bypassedand an error message is printed (see CompilationErrors). Either the size of the source program orthe number of symbols used must be decreased, orthe program must be compiled on a machine of largerstorage capacity.SYMBOL TABLEThe Symbol Table contains entries for variables,constants, statement numbers, various compilergeneratedlabels, and compiler-generated temporarystorage locations.The first entry of the Symbol Table occupies thethree highest-addressed words of the String Area,1. e. , the 3 words just below the first word of theFORTRAN Communications Area. The second entryis positioned in the lower-numbered words adjacentto the first entry, etc.During the initialization of the Symbol Table inphase 1, three words are reserved for the firstSymbol Table entry. This entry is not made, however,until phase 3. From this point the size of theSymbol Table varies from phase to phase until itachieves its largest size in phase 18. Its size always.includes the three words reserved for the nextSymbol Table entry.During phases 3 through 18, the Symbol Table containsvariables, constants, and statement numbers.Information for these entries has been removed fromthe statement string and has been replaced by theaddress of the ID word of the corresponding SymbolTable entry. Also, the Symbol Table contains thevarious compiler•generated labels and temporarystorage locations used in compilation.During the output phases, 19 through 26, theseentries in the Symbol Table are replaced by objectprogram addresses that are inserted into the objectcoding by phase 26.FormatAll entries in the Symbol Table consist of threewords -- an ID word and two Name-Data words.The entries for dimensioned variables are exceptional,however, in that they are six-word entries, theadditional three words containing the dimensioninformation.The ID word occupies the lowest-addressed wordof the three word entry. The Name-Data wordsoccupy the two higher-addressed words.A typical three-word entry is illustrated in thefollowing example of the entry for the integer constant290.ID Word Data Word 1 Data Word 22 9 0 blank blank111000000000000001011001011100111010000000000000000 ILowest-Addressed Highest-AddressedWordWordEntry in hexadecimal form —E000 65CE 0000The entry for the subprogram name COUNT wouldappear as:ID Word Name Word 1 Name Word 2COUN T1000000001000000011000011010110100111000101011000111Lowest-Addressed Highest-AddressedWordWordEntry in hexadecimal form - C080 86B4 C56378