PL/0编译器源码实现-Pascal语言

program   pl0; 
    {PL0   compiler   with   code   generation} 
    const 
        al=10;             {length   of   identifiers} 
        norw=16;         {number   of   identifiters}     {if   then   else   &   repeat   until} 
        nmax=14;         {max   number   of   digits   in   number} 
        amax=2047;     {?max   address   or   renge   of   number} 
        levmax=3;       {max   depth   of   block   nesting} 
        txmax=100;     {max   length   of   identifier   table} 
        cxmax=200;     {max   length   of   code   array} 
    type 
        symbol=(nul,ident,number,plus,minus,times,slash,oddsym, 
                        eql,neq,lss,leq,grt,geq,lparen,rparen,comma,colon,{arrar} 
                        semicolon,period,becomes,beginsym,endsym,ifsym, 
                        thensym,elsesym,whilesym,repeatsym,untilsym, 
                        writesym,readsym,dosym,callsym, 
                        constsym,varsym,procsym);   {if   then   else   &   repeat   until} 
        symset=set   of   symbol; 
        alfa=string[al]; 
        object0=(constant,variable,intarray,procedur);   {arrar} 

        fct=(lit,opr,lod,sto,cal,int,jmp,jpc); 
        instruction= 
            record 
                f:fct;                   {function   code} 
                l:0..levmax;       {level} 
                a:0..amax 
            end; 
    var 
        fin:text;               {the   source   file} 

        ch:char;                 {the   next   char} 

        sym:symbol; 
        a,id:alfa;             {arrar} 
        num:integer; 
        l,h:integer;                     {arrar} 
line:string[80];     {current   line   of   source   file} 
        ln:integer;               {number   of   current   line} 
        ll:integer;               {length   of   current   line} 
        cc:integer;               {position   of   ch   in   line} 


        cx:integer;               {point   to   the   next   instruction   in   code} 
        code:array[0..cxmax]   of   instruction; 
  
    
        word:array[1..norw]   of   alfa; 
        wsym:array[1..norw]   of   symbol; 
        ssym:array[ '   '.. '^ ']   of   symbol; 

        mnemonic:array[fct]   of   string[5]; 

        declbegsys,statbegsys,facbegsys:symset; 

        table:array[0..txmax]   of 
            record 
                name:alfa; 
                case   kind:object0   of 
                    constant:(val:integer);