CS212 Spring 2002
3/27/2002
Lecture 9: Wrap Up on FBR; Translation
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[0] Announcements:
+ did anyone start Part 3?
+ reading: Brookshear 5.1, 5.4
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[1] Summary from last time:
+ completed example in [7] (Lecture 7)
+ didn't formally get to live examples
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[2] Overview for today:
+ reminder of complete sam-code for functions
+ explanation of examples
+ more details on compilers and intro to syntax trees
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[3] Generic sam-code:

// PROGRAM EXECUTION:


PUSHIMM 0


PUSHFBR


PUSHIMM 1


POPFBR


JSR main


POPFBR


STOP


// FUNCTION EXECUTION:

label:       


ADDSP n  


STOREOFF -1


ADDSP -n


JUMPIND




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// FUNCTION INVOCATION (calling function f):


PUSHIMM 0 // or ADDSP 1


PUSHFBR


PUSHSP


PUSHIMM n+1


SUB


POPFBR


JSR f


ADDSP -n


POPFBR


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[4] Examples

+ see a.sam, b.sam, c.sam from Lecture 8
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[5] Language Implementation

+ see section 5.4 in optional textbook
+ showing a bit more detail on what's going on
+ TRANSLATOR vs COMPILER? see pg 228
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[6] Translation

+ TRANSLATION: converting a program from one language to another
               SOURCE PROGRAM gets translated into OBJECT PROGRAM
+ process of translation:

  source       lexical       parser     code         object
  program      analyzer                 generator    program











+ note: steps are usually intertwined

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[7] Lexical Analysis

+ LEXICAL ANALYSIS: recognizing which strings of symbols from the 
                    source program represent a single entity
+ TOKEN: lexical unit, or one of the entities recognized by the lex analyzer

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[8] Parsing

+ PARSING: process of identifying the grammatical structure of the program
           and recognizing the role of each component

+ formatting:
  FIXED-FORMAT LANGUAGE: appearance and position matters for parser
  FREE-FORMAT LANGUAGE: positioning of statements is irrelevant

+ SYNTAX DIAGRAMS:
  - see pp 257-258
  - graphical ways of representing the syntax rules
  - TERMINALS ("finished" nodes) and NONTERMINALS (need further expansion)

+ PARSE TREE:
  - see pp 259-260
  - graphical ways of representing how code conforms to syntax
  - represents parser's understanding of program's grammar
    ex) x + y

       Expr
       /|\
   Term + Term
    |      |
    x      y

+ SYMBOL TABLE:
  - storing variable info
  - see book for details

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[9] Code Generation

+ CODE GENERATION: process of constructing the machine-language instructions
                   to simulate the statements recognized by the parser

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[10] Linking and Loading

+ terms pop up quite a bit with C/C++ programming
+ see pp 262-264
+ LINKING: connections to needed operating system utilities
+ LOADING: put complete executable program into memory

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