Program Logic Manual - All about the IBM 1130 Computing System

entry is found, no new entry is made. The constantoperator, a special code Indicating that the followingword is the Symbol Table address of a constant,followed by the Symbol Table address of the constantalready entered is inserted into the statementstring in place of the constant.If no previous entry in the Symbol Table is found,the converted constant is added to the Symbol Table.The constant operator along with the Symbol Tableaddress replaces the constant in the statement string.The statement string is closed up following the alterationof the string.Errors DetectedThe following errors are detected by phase 6: 23and 50.PHASE 7• Checks the syntax of DEFINE FILE, CALL EXIT,and CALL LINK statements.• Determines the defined file specifications.All variable names in DEFINE FILE, CALL LINK,and CALL EXIT statements are checked for validityand are added to the Symbol Table. All valid constantsare converted to binary and are added to theSymbol Table.Phase 7 checks to ensure that a DEFINE FILEstatement does not appear in a subprogram.This phase computes the file definition specifications,that is, a DEFINE FILE Table consisting ofone entry for each unique file. Each entry consistsof the file number, the number of records per file,the record length, the associated variable, a blankword for insertion of the file's sector address at thetime the program is loaded for execution, the numberof records per sector, and the number of diskblocks per file. A count is kept in the DFCNT word(word 17) in the FORTRAN Communications Areaof the number of files defined.Errors DetectedThe errors detected by phase 7 are: 3, 70, 71, 72,73 and 74.PHASE 8• Places variables and integer constants into theSymbol Table.• Places parameters from statement function statementsinto the Symbol Table.• Replaces operators with pointers to the ForcingTable to be used in phase 16.• Converts the left parenthesis of subscripts to aspecial dimension indicator.Phase 8 checks the variable names found in the statementstring for validity. Valid variables are addedto the Symbol Table. A second check is made to ensurethat all variable names conform to the implicitor explicit mode specifications (real and integer).Integer constants are also added to the Symbol Table,provided they are unique. However, integer constantsthat are found in subscript expressions arenot added to the Symbol Table until a later phase.When adding names and constants to the SymbolTable, phase 8 replaces them in the string by theaddress of their respective Symbol Table entries,except if they are found in subscript expressions.The address replacing a constant or name is theaddress of the ID word of the Symbol Table entryfor that constant or name.Internal statement numbers are located in theSymbol Table and are replaced by the address of theircorresponding Symbol Table entries; those statementnumbers not found in the Symbol Table (i. e. ,not previously entered) are in error.Phase 8 changes the ID word of the statementfunction statement, until now identical to that of anarithmetic statement, to the statement function type.Also, the statement function name and the parametersof statement functions are added to the SymbolTable. These entries in the Symbol Table are distinguishedby their lack of a sign bit in the secondword of the name.During phase 8, the left parenthesis on subscriptsis changed to a special left parenthesis operator thatindicates the order of the dimension that follows.This phase also converts all operators, exceptthose in subscript expressions, from the 6-bitEBCDIC representation to a pointer value. Thispointer value is derived from the Forcing Table. Theconversion is done in preparation for the Scan Phase,Section 11. FORTRAN Compiler 85