EEN519 Study Guide (19th November 1998)

• Traditional Fortran:
  • General syntax
  • Primitive design decisions and the problems they cause:
    • automatic declarations, ignoring spaces, no reserved words, etc.
  • Basic Statements and Data types: how to write programs
  • Memory management
    • static activation records allocated by compiler
    • impossibility of recursion
    • impossibility of global variables
    • common blocks
    • mechanism of subroutine and function call
    • call by reference vs. Call by value
• Characteristics of variables:
  • Static vs. Dynamic / Stack vs. Heap Allocation
  • Free vs. Bound
  • Contents of an activation record
    • Static link and Dynamic link
    • Problems with Dynamic Free variables
  • Stack Frame as implementation of Activation Records
    • Local variable access relative to Frame Pointer
  • Scope and Extent
  • Dangling References (problems of, and how to avoid them by sensible language design)
    • Caused by function-type variables and nested functions in the same language
    • Caused by generating pointer to local variable
  • Parameter passing methods:
    • call by Value
    • call by Reference
    • call by Result
    • call by Value-Result
    • call by Constant
    • and their main features:
      • efficiency, simplicity, potential for aliassing

==================== First Test, 1st October ==============================

• Grammars and Syntax
  • BNF meta-language for describing the syntax of languages
  • Ambiguity
    • Exactly what it means
    • Common examples of ambiguous programming language definitions
    • The "Dangling Else" problem, and the various ways it is fixed
  • Grammars for expressions that specify order of evaluation
• The power of a programming language
  • Proving that every structured program can be written in an unstructured language
  • Proving that every unstructured program can be written in a structured language
    • i.e. as far as expressing algorithm structure is concerned, C and Fortran are equal
  • Implementing recursion in languages that do not support it
  • Implementing data structures in languages that do not support them.
  • What the real differences between Fortran and C are:
    • (technical): no dynamic allocation in Fortran,
      • so recursion/data structure schemes will fail for large inputs
    • (practical): C is a higher level, more abstract language,
      • so programming is easier and therefore more reliable
• Prolog - A very high level language
  • General idea: just express your design as logical rules, no algorithm needed
  • Be able to write Prolog definitions for simple-ish logical rules,
  • Be able to understand Prolog definitions written by others.
  • Strengths and limitations: The problem of negation.
• Co-routines
  • The general idea:
    • functions that can return control without exiting
    • (recall the enumeration/operation in charge example)
    • The need to maintain a separate stack space for each coroutine
  • How they are programmed:
    • start and resume as fundamental operations
    • co-routines almost act as parallel/concurrent threads of execution

==================== Second Test, 24th November ==============================

• Compilers
  • General structure
  • Design of principal parts
• Lisp (possibly, just the very basics)

=============== Final Examination, 2pm Thursday 10th December ================