Midterm I

Name: ________________________________________________

ID Number: ___________________

Please write your answers in the space provided! Make sure your name is in the same form as it appears on your University ID card! Illegible and excessively long answers will be penalized! This exam is open-book, open-notes, closed neighbor! This exam is worth 1/10 of the final grade (10 points; allocate 4-5 minutes per point).

1. Hand assemble the following EAL code, and show what goes in the symbol table. For those lines of code that cause data to be stored in memory, show the memory address that is changed and the value stored in memory. There are many extra blanks! Do not fill in anything unused symbol table entries or next to lines that assemble nothing into memory. (2 points)

    line     hexadecimal     source
   number  location  value    text
   
     1    ________  _______       B    13           symbol table
                                                   symbol    value
     2    ________  _______       B    #13
                                                 ________  ________
     3    ________  _______  ; Commentary
                                                 ________  ________
     4    ________  _______       B    C 
                                                 ________  ________
     5    ________  _______  A:   B    B
                                                 ________  ________
     6    ________  _______       B    A
   
     7    ________  _______  B    =    10
    
     8    ________  _______  C:
   

   For a bit more credit, circle the line numbers of the lines that cannot be properly processed on the first pass of a two pass assembler. (0.5 points)

2. Consider this bit of EAL code (2 points):

   	MACRO	FIDDLE P	a) What is the actual parameter to FIDDLE? __________
   	OFFEND	P)-(P
   	ENDMAC		b) What is the actual parameter to OFFEND? __________
   	MACRO	OFFEND Q	c) What does the body of OFFEND expand to? __________
   	B	(1+Q+1)
   	ENDMAC		d) What value gets assembled into memory? __________
   	FIDDLE	5

    

   Name: ________________________________________________

    

    

3. Hand assemble the following EAL code, and show what goes in the symbol table. For those lines of code that cause data to be stored in memory, show the memory address that is changed and the value stored in memory. There are many extra blanks! Do not fill in anything unused symbol table entries or next to lines that assemble nothing into memory. (2 points)

    line     hexadecimal     source
   number  location  value    text
   
     1    ________ ________       W    8
   
     2    ________ ________  Z:                     symbol table
                                                  symbol    value   abs/rel
     3    ________ ________  .    =    .+2
                                                 ________  ________  ____
     4    ________ ________  Y:   W    Z 
                                                 ________  ________  ____
     5    ________ ________  X:          
                                                 ________  ________  ____
     6    ________ ________  .    =    Z
                                                 ________  ________  ____
     7    ________ ________       W    Y
    
     8    ________ ________  .    =    X
   
     9    ________ ________       W    X
   

   For a bit more credit, for each symbol in the above symbol table, indicate whether it would be absolute or relocatable. (0.5 points)

    

    

    

    

4. Hand assemble the following bit of EAL code, showing what goes in memory. (2.0 points)

           MACRO X I             0000: _________
             B I
             IF I > 1            0001: _________
               X (I-1)
             ENDIF               0002: _________
           ENDMAC
                                 0003: _________
           X 0
           X 1                   0004: _________
           X 2
           X 3                   0005: _________
   

    

    

   Name: ________________________________________________

    

    

5. Consider the following fragment from the grammar for C:

   <declaration> ::= <type> <name> [ = <initializer> ] ;
   <initializer> ::= <value> | [ <initializer> { , <initializer> } ]

   Note the use of boldface to distinguish terminal symbols from metasymbols. Fill in the blanks in the following C code fragment to complete the skeleton for a parser for this fragment. (2 points)

   void parse_declaration()
   {
   
       __________________________________
       parse_name();
       if (lex_this == '=') {
           lex_scan();        /* scan over = */
   
           _________________________________
       }
       if (lex_this != ';')
           EXCEPT_RAISE( parse_error );
       lex_scan();        /* scan over ; */
   }
   
   void parse_initializer()
   {
       if (lex_this != ___________________ ) {
           parse_value();
       } else {
           do {
               lex_scan;      /* scan over ________ or _______ */
   
               _________________________________
   
           while (lex_this == ____________________ );
           if (lex_this != ']')
               EXCEPT_RAISE( parse_error );
           lex_scan();        /* scan over ________ */
       }
   }