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PROGRAM PL0(INPUT,OUTPUT);
CONST
  AL=10;{标识符长度}
  NORW=15;{保留字个数}
  TXMAX=100;{标识符表长度}
  NMAX=14;{数中数字的最大个数}
  AMAX=2047;{最大地址}
  LEVMAX=3;{分程序嵌套的最大深度}
  CXMAX=200;{目标代码数组的大小}
TYPE
  SYMBOL=(NUL,IDENT,NUMBER,PLUS,MINUS,TIMES,SLASH,ODDSYM,EQL,NEQ,LSS,
         LEQ,GTR,GEQ,LPAREN,RPAREN,COMMA,SEMICOLON,PERIOD,BECOMES,ELSESYM,
         BEGINSYM,ENDSYM,IFSYM,THENSYM,WHILESYM,WRITESYM,READSYM,DOSYM,
         CALLSYM,CONSTSYM,VARSYM,PROCSYM,PROGSYM);
  ALFA=PACKED ARRAY[1..AL] OF CHAR;
  BJECT=(CONSTANT,VARIABLE,PROCEDUR);
  SYMSET=SET OF SYMBOL;
  FCT=(LIT,OPR,LOD,STO,CAL,INT,JMP,JPC);
  INSTRUCTION=PACKED RECORD
                       F:FCT;
                       L:0..LEVMAX;
                       A:0..AMAX;
                    END;
{LIT 0,A:取长量a
  OPR 0,A:执行运算a
  LOD 1,A:取变量(相对地址为;层差为1)
  STD 1,A:存变量
  CAL 1,A:调用过程(入口地址为a;层差为1)
  INT 0,A:运行栈S的增加a
  JPM 0,A:转移到指令地址a
  JPC 0,A;条件转移到指令地址a处}

  VAR
   cchh:char;
   CH:CHAR;{当前字符}
   SYM:SYMBOL;{当前符号}
   ID :ALFA;{当前标时符}
   NUM:INTEGER;{当前数}
   II:INTEGER;
   CC:INTEGER;{字符计数}
   LL:INTEGER;{行长}
   LNUM:INTEGER;
   KK:INTEGER;
   CX:INTEGER;{目标代码下标}
   ERR:INTEGER;
   LINE:ARRAY[1..81] OF CHAR;
   A:ALFA;
   SC:TEXT;
   SOUCFILE:STRING;
   FNAME:ALFA;
   CODE:ARRAY[0..CXMAX] OF INSTRUCTION;{目标代码区}
   WORD:ARRAY[1..NORW] OF ALFA;{保留字表}
   WSYM:ARRAY[1..NORW] OF SYMBOL;{保留字机内表示表}
   SSYM:ARRAY[CHAR] OF SYMBOL;{运算符,界限符机内表示表}
   MNEMONIC:ARRAY[FCT] OF PACKED ARRAY[1..5] OF CHAR;
   DECLBEGSYS,STATBEGSYS,FACBEGSYS:SYMSET;
   TABLE:ARRAY[0..TXMAX] OF
          RECORD
           NAME:ALFA;
            CASE KIND:BJECT OF
              CONSTANT:(VAL:INTEGER);
              VARIABLE,PROCEDUR:(LEVEL,ADR,SIZE:INTEGER);
             END;
   PROCEDURE ERROR(N:INTEGER);
    BEGIN
     WRITE('ERROR IN LINE', LNUM,id);
     WRITELN('*******',N:2);
     READ(CCHH);
     ERR:=ERR+1
   END;{ERROR 过程结束}
  PROCEDURE GETSYM;{词法分析}
   VAR
    I,J,K:INTEGER;
  PROCEDURE GETCH;{读字符}
   BEGIN
    IF CC=LL
     THEN BEGIN
           IF EOF (SC)
            THEN  WRITE('PROGRAM INCOMPLETE');
           LL:=0;CC:=0; WRITE(CX:4,' ');
           WHILE NOT EOLN(SC) DO
            BEGIN
             LL:=LL+1;
             READ(SC,CH);WRITE(CH);
              LINE[LL]:=CH
            END;
          WRITELN;LNUM:=LNUM+1;LL:=LL+1;
          READ(SC,LINE[LL]);READ(SC,CH);LINE[LL]:=' '
        END;
      CC:=CC+1;
      CH:=LINE[CC]
    END;{GETCH 过程结束}