Compilers Translators

, 06 2005 , 11

, , .

T ( ) .

COMPILERS TRANSLATORS ( )

.

, (loop) - - , .

Compilers Translators , :H (Lexical analysis) .

H (Syntactical analysis) .

, (Code genertion) , , H. Y.

(..) .

:

(grammar syntax),

T (semantics)- (meaning)

:

(grammar) (syntax)

(mening) (semantics).

To , , '', , ' '.

..., , ... FORTRN ( BSIC) :

=B+C

. :

=+-)5.6.7

, .

BACKUS-NAUR Backus-Naur Form (BNF) , ., BNF () ::= , - . (recursion), number .TA: : (digit) : :=0|1|2|3|4|5|6|7|8|9 (letter) ::=|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z

: 0 1 2 .. . 9 , ; : .. . .

:

:

:=

:

:=

, HGK123N 135GKL123N, .

, BNF ( ): :=|

: , .

, ( ), (recognition tree), . Parsing ( - ).

.. 4338 (to be parsed) : ,

:=

, , . , .

.

: .. ALGOL68 (syntax) (semantics) .

(LEXICAL ANALYSIS)

- - , - ( ) , PASCAL ( ; )... : var n,c : integer ;

.

, ( ... Pascal):

program average;var n,c: integer: x,y: real; begin read(n); x=0; for c: 1 to n dobegin read(y); if y49.25then writeln (y, 'IS OUT OF RANGE') else x:=x+yend;writeln('AVERAGE=, x/n)end.

, : , , , IF, THEN, ELSE, END . , . COMPILER , ., : 15, 0, 771, 5.54367 . (strings) (quote marks) - .-, , , .

(), ( ).

(number table). (string table), (token table), , tokens , , (1, 2, 3 4) () tokens

1, , Pascal, . Pascal :

-1

orintegerrealwritelnsincossqrtRead2526272829303132

, 2 (number table) Token (pointer) . .. , :-2

To token (2,3) 3.5

, 3 (string table) :-3

To token (3,2) "AVERAGE ="

StringLocation12TableValueIS OUT OF RANGEAVERAGE=

() , 4 (nametable) :

-4

To token (4,4) 'x' , .

Name 12345TableAVERAGEncxy

Token token, , , , . , token :

, ( ... Pascal):

program average; var n,c: integer; ! n x,y: real; ! 3.5 begin read(n); x=0; ! 49.25for c: 1 to n dobegin read(y); if y49.25then writeln (y, 'IS OUT OF RANGE') else x:=x+yend;writeln('AVERAGE=' ,x/n)end.

1 2 3 4

compiler program end. TokenTo 47o Token 2 4 49.25, 53 Token 3 1 strings IS OUT OF RANGE

, 13, 37, 41, 45, 51 60, Token 4 5 , ( ) , . , , strings Tokens