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Department of Computer Science and Engineering

Course Name : Principles of Programming language Course Number : Course Designation : Core Prerequisites : C, C++ & JAVA

III B Tech I Semester

(2015-2016)M.MADHAVI

Associate Professor

SYLLABUS

Unit I

Preliminary Concepts: Reasons for studying, concepts of programming languages, Programming domains, Language Evaluation Criteria, influences on Language design, Language categories, Programming Paradigms Imperative, Object Oriented, functional Programming , Logic Programming .Programming Language ImplementationCompilation and Virtual Machines, programming environments.

Syntax and Semantics: general Problem of describing Syntax and Semantics, formal methods of describing syntax - BNF, EBNF for common programming languages features, parse trees, ambiguous grammars, attribute grammars

Unit II

Data types: Introduction, primitive, character, user defined, array, associative, record, union, pointer and reference types, design and implementation uses related to these types .Names, Variable, concept of binding, type checking, strong typing, type compatibility, named constants, variable initialization.

Expressions and Statements: Arithmetic relational and Boolean expressions, Short circuit evaluation mixed mode assignment, Assignment Statements, Control Structures Statement Level, Compound Statements, Selection, Iteration, Unconditional Statements, guarded commands.

Unit III

Subprograms and Blocks: Fundamentals of sub-programs, Scope and lifetime of variable, static and dynamic scope, Design issues of subprograms and operations, local referencing environments, parameter passing methods, overloaded sub-programs, generic sub-programs, parameters that are sub-program names, design issues for functions user defined overloaded operators, co routines.

Abstract Data types: Abstractions and encapsulation, introductions to data abstraction, design issues, language examples, C++ parameterized ADT, object oriented programming in small talk, C++,Java,C#,Ada95.

Unit IV

Concurrency: Subprogram level concurrency, semaphores, monitors, massage passing, Java threads, C# threads.

Exception handling: Exceptions, exception Propagation, Exception handler in Ada, C++ and Java.

Unit V

Logic Programming Language: Introduction and overview of logic programming, basic elements of prolog, application of logic programming.

Functional Programming Languages: Introduction, fundamentals of FPL, LISP, ML, Haskell, application of Functional Programming Languages and comparison of functional and imperative Languages.

TEXT BOOKS & OTHER REFERENCES

Text Books

1.

Concepts of Programming Languages Robert .W. Sebesta 6/e, Pearson Education.

2.

Programming Languages Louden, Second Edition, Thomson.

Suggested / Reference Books

3.

4.

5.

Websites References

1.

http://freevideolectures.com/University/IIT-Madras/Web-Designing/Subject/Page1

2.

http://en.wikipedia.org/wiki/Programming_language

3.

http://www.learnerstv.com/video/Free-video-Lecture-1950-Computer-Science.html

4.

http://www.openculture.com/freeonlinecourses

5.

http://www.dmoz.org/desc/Computers/Programming/Languages

6.

http://freevideolectures.com/Course/2331/Building-Dynamic-Websites/2

7.

http://www.saylor.org/courses/cs404/rief

Time Table

Room No:

W.E.F:

Class Hour

Time

1

2

3

4

12:20 1:10

LUNCH BREAK

5

6

7

9:00 -09:50

09.50 10:40

10:40 11:30

11:30 12: 20

1:10 2:00

2:00 2:50

2:50 3:40

MON

TUE

WED

THU

FRI

SAT

PROGRAM EDUCATIONAL OBJECTIVES (PEOs)

PEO1

The Graduates are employable as software professionals in reputed industries.

PEO2

The Graduates analyzeproblems by applying the principles of computer science, mathematics and scientific investigation to design and implement industry accepted solutions using latest technologies.

PEO3

The Graduates work productively in supportive and leadership roles on multidisciplinary teams with effective communication and team work skills with high regard to legal and ethical responsibilities.

PEO4

The Graduates embrace lifelong learning to meet ever changing developments in computer science and Engineering.

PROGRAM OUTCOMES (POs)

PO1

An ability to communicate effectively and work on multidisciplinary teams

PO2

An ability to identify, formulate and solve computer system problems with professional and ethical responsibility.

PO3

A recognition of the need for, and an ability to engage in life-long learning to use the latest techniques, skills and modern engineering tools

PO4

The broad education necessary to understand the impact of engineering solutions in a global, economic, environmental and social context

PO5

An ability to apply knowledge of mathematics, science, and computing to analyze, design and implement solutions to the realistic problems.

PO6

An ability to apply suitable process with the understanding of software development practice.

Course Outcomes:

CO1

They will be able to Know the modular and object oriented programming

CO2

They will able to write complier programs

CO3

They will be to know logical and functional programming technique

CO4

They will able to develop concurrency programming

MAPPING OF COURSE OBJECTIVES & COURSE OUT COMES WITH

POs & PEOs

Course Outcomes

POs

PEOs

CO1

PO1

PEO2

CO2

PO5

PEO1

CO3

PO5

PEO1

CO4

PO2

PEO2

COURSE SCHEDULE

Distribution of Hours Unit Wise

Unit

Topic

Chapters

Total No. of Hours

Book1

Book2

I

Reasons for studying, concepts of programming languages, Programming domains

Syntax and Semantics

Ch1,2

Ch3,4,5,6,7

14

II

Data types

Expressions and Statements

Ch8,9

-

14

III

Subprograms and Blocks

Abstract Data types

Ch10, 11

-

13

IV

, Concurrency, Exception handling

Ch12,13

-

12

V

Logic Programming Language,

LISP, ML, Haskell

Ch19,20

-

12

Contact classes for Syllabus coverage

65

Tutorial Classes : 08 ; Online Quiz : 1 per unit

Descriptive Tests : 02 (Before Mid Examination)

Revision classes :1 per unit

Number of Hours / lectures available in this Semester / Year

65

The number of topic in every unit is not the same because of the variation, all the units have an unequal distribution of hours

Lecture Plan

S. No.

Topic

Date of Completion

Unit-1

1

Reasons for studying, concepts of programming languages

TB-1

2

Programming domains

TB-1

3

Language Evaluation Criteria

TB-1

4

Influences on Language design, Language categories

TB-1

5

Programming Paradigms Imperative, Object Oriented

TB-1

6

functional Programming , Logic Programming

TB-1

7

Programming Language Implementation

TB-1

8

programming environments

TB-1

9

General Problem of describing Syntax and Semantics

TB-1

10

Formal methods of describing syntax BNF

TB-1

11

EBNF for common programming languages features

TB-1

12

Parse trees

TB-1

13

Ambiguous grammars

TB-1

14

Attribute grammars

TB-1

Unit-II

TB-1

15

Data types: Introduction, primitive, character

TB-1

16

User defined, array, associative, record

TB-1

17

Union, pointer and reference types

TB-1

18

Design and implementation uses related to these types

TB-1

19

Names, Variable, concept of binding

TB-1

20

Type checking, strong typing, Type compatibility

TB-1

21

Named constants, variable initialization

TB-1

22

Arithmetic and relational expressions

TB-1

23

Boolean expressions

TB-1

24

Short circuit evaluation mixed mode assignment

TB-1

25

Assignment Statements

TB-1

26

Control Structures Statement Level

TB-1

27

Compound Statements, Selection

TB-1

28

Iteration, Unconditional Statements

TB-1

Unit-III

TB-1

29

Fundamentals of sub-programs

TB-1

30

Scope and lifetime of variable, static and dynamic scope

TB-1

31

Design issues of subprograms and operations

TB-1

32

Local referencing environments, Parameter passing methods

TB-1

33

Overloaded sub-programs

TB-1

34

Parameters that are sub-program names,

TB-1

35

generic sub-programs

TB-1

36

Design issues for functions

TB-1

37

Abstractions and encapsulation

TB-1

38

Language examples

TB-1

39

Java, C#, Ada 95, Subprogram level concurrency

TB-1

40

Massage passing, Java threads

TB-1

41

Object oriented programming in small talk

TB-1

42

C++

TB-1

43

C# threads

TB-1

44

C++ parameterized ADT

TB-1

Unit-IV

TB-1

45

semaphores, Monitors

TB-1

46

Exceptions

TB-1

47

Exception handler in Ada

TB-1

48

Exception handler in C++

TB-1

49

exception Propagation

TB-1

50

Exception handler in Java

TB-1

51

Introduction to logic programming

TB-1

52

overview of logic programming

TB-1

53

Basic elements of prolog

TB-1

54

Application of logic programming

TB-1

Unit-V

TB-1

55

Introduction to logic programming

TB-1

56

overview of logic programming

TB-1

57

Basic elements of prolog

TB-1

58

Application of logic programming

TB-1

59

Fundamentals of FPL

TB-1

60

LISP

TB-1

61

ML

TB-1

62

Haskell

TB-1

63

Haskell

TB-1

64

Application of Functional Programming Languages

TB-1

65

Comparison of functional and imperative Languages

TB-1

Date of Unit Completion & Remarks

Unit 1

Date

:

__ / __ / __

Remarks:

________________________________________________________________________

________________________________________________________________________

Unit 2

Date

:

__ / __ / __

Remarks:

________________________________________________________________________

________________________________________________________________________

Unit 3

Date

:

__ / __ / __

Remarks:

________________________________________________________________________

________________________________________________________________________

Unit 4

Date

:

__ / __ / __

Remarks:

________________________________________________________________________

________________________________________________________________________

Unit 5

Date

:

__ / __ / __

Remarks:

________________________________________________________________________

________________________________________________________________________

Unit Wise Assignments (With different Levels of thinking (Blooms Taxonomy))

Note: For every question please mention the level of Blooms taxonomy

Unit 1

1.

Write about linker? Explain the responsibilities of the linker? L1

2.

Explain the different aspects of cost of a programming language? L4

3.

What common programming language statements in your opinion is most deter to readability? L3

4.

Define CFG. State whether CFG is a language generator or recognizer? L1

5.

Explain with an example how operator associativity can be incorporated in grammars?

L4

Unit 2

1.

Define strong typing. Discuss how type checking is enforced in Fortran95, Ada, C, C++, and Java. What do you mean by coercion, how does it effect strongly typed languages? L1

2.

Describe the process of Array initialization? L5

3.

Explain all of the difference between subtypes and derived types? L4

4.

Compare and Contrast union, free union and discriminated union? L4

5.

What are the advantages and disadvantages of allowing mixed-mode arithmetic expressions? L4

6.

Explain the problems associated with Unconditional Branching? L4

7.

List out Errors that can occur in Expression Evaluation? L1

Unit 3

1.

Explain the Various Design issues that are involved in functions? L6

2.

Difference between procedures and functions? L4

3.

What is the primary problem with using semaphores to provide synchronization? L3

4.

In what different places can the definition of a C++ member function appears? L4

5

What is a C++ Name space? What is it purpose? L2

Unit 4

1.

Explain in detail about Exception handling in Ada? L4

Unit 5

1.

Explain the difference between CONS, LIST and APPENED? L4

2.

Write a Lisp function Fib (n) that computes a nth Fibonacci number? L3

Unit Wise Case Studies (With different Levels of thinking (Blooms Taxonomy))

Note: For every Case Study please mention the level of Blooms taxonomy

Unit 1

1.

Was the first high level programming language you learned, implemented within pure interpreter, a hybrid implementation system or a compiler? If yes, justify? L5

2.

Enumerate evaluation criteria of some programming language? L4

3.

Many contemporary languages allows to kinds of comments: one in which delimiters are used both ends (multiple-line comments) and one in which a delimiter marks only the beginning of the comment (one-like comments). Discuss the advantage and disadvantages of each of these with respect to our criteria? L3

4.

= L4

A|B|C

+

|

*

|

()

|

Using the above grammer, show a parse tree and a left most derivation for each of the following statemtns.

1) A=(A+B)*C

2) A=B+C+A

3) A=A*(B+C)

4) A=B*(C*(A+B))

Unit 2

1.

Assume the following Ada program was complied and executed using static scoping rules. What value of x is printed in procedure sub1? Under dynamic scoping rules, what value of x is printed in procedure sub1? L3

procedure main is

x: integer;

procedure sub1 is

begin

put(x)

end;

procedure sub2 is

x:integer;

begin

x:=10

sub1

end;

begin

x:=5;

sub2

end;

2.

Some programming languages are typeless what are the obvious advantages and disadvantages of having no types in a language? L2

3.

Write a c program the does a large number of references to element of two dimensional arrays, using only subscripting write a second program that does the same operations but uses pointers and pointer arithmetic for the storage mapping function to do the array reference. Compare the time efficiency of the two programs. Which of the two programs is likely to be more reliable? Why? L1

4.

Let the function fun is defined as L3

int fun(int *k)

{

*k+=4;

return 3 *(*k)-1;

}

Suppose fun is used as follows:

void main()

{

int i=10,j=10;sum1,sum2;

sum1=(i/2)+fun(&i);

sum2=fun(&j)+(j/2);

What are the values of sum1 and sum2

a) If the operands in the expressions are evaluated left to right?

b) If the operands in the expressions are evaluated right to left?

Unit 3

1.

Consider the following program L4

void swap(int a, int b)

{

int temp;

temp=a;

a=b;

b=temp;

}

void main()

{

int value=2,list[5]={1,3,5,7,9};

swap(value, list[0]);

swap(list[0], list[1]);

swap(value, list[value]);

}

For each of the following parameters passing methods, what are all of the values of the variables value and list after each of the three calls to swap?

a) Pass by value

b) Pass by reference

c) Passed by value-result

2.

What dangers are avoided in Java and C# by having implicit garbage collector, relative to C++? L2

3.

What is the best action a system can take when deadlock is detected? L2

Unit 4

1.

In a language with exception handling facilities, it is common to have more subprograms include an error parameter, which can be set to same value representing ok what advantage does linguistic exception handling facility like that of Ada have over this method? L4

Unit 5

1.

Design the quick sort algorithm in scheme language? L6

2.

Construct the scheme function that removes the last element from a give list? L6

Unit Wise Important Questions (With different Levels of thinking (Blooms Taxonomy))

Note: For every question please mention the level of Blooms taxonomy

Unit 1

1.

Explain in detail various phases in the process of compilation? L4

2.

Give an example of how aliasing deters reliability? L3

3.

Why it is useful for a programmer to have some background in language design? L3

4.

Difference between compilation and interpretation? L4

5.

How can knowledge of programming language characteristics benefit the whole computing community? L2

6.

What role does the symbol table play in a complier? L4

7.

In what fundamental way do operational semantics and denotational semantics differ?

L4

8.

Develop an unambiguous grammar that describes the if statement? L3

9.

Discuss the following? L2

1) Assignment statements

2) Logical pretest loops

10.

In what fundamental way do the operational and denotional semantics differ? L3

Unit 2

1.

Define the following? L1

a) Stack Dynamic

b) Explicit Heap Dynamic

c) Implicit Heap Dynamic

d) Static

2.

Describe how the pointers used in C and C++ with examples? L1

3.

Explain pointers, reference types, design issues of pointers, operations on pointers, pointer problems and implementation of pointer and reference types? L4

4.

Difference between Static and Dynamic strings? L4

5.

How does operand evaluation order interact with functional side effects? L3

6.

Discuss the benefits of operator overloading? L2

7.

Explain in detail multiple selection constructs? L4

8.

Explain about the iteration based Data structures? L4

Unit 3

1.

What are the modes, the conceptual models of transfer, the advantages and disadvantages of pass by value, pass by result, pass by value-result and pass by reference parameter passing methods? L3

2.

Define Shallow and deep binding for referencing environment of subprograms that have been passed as parameter? L1

3.

Explain the considerations for choosing parameter passing methods? L4

4.

Explain, how multi dimensional arrays can passed as arguments in Ada language? L4

Unit 4

1.

Classify the difference Physical and logical concurrency? L3

2.

Outline the three possible levels of concurrency in programs? Explain? L2

3

Write short notes on C# threads? L1

4

Discuss the different states a task can be? Explain? L2

5.

Explain the following with examples? L4

a) Exception handler

b) Disabling an Exception

c) Continuation

6.

Explain detailed compassion of Exception handling capablites of C++ and those of Java? Explain the following with examples? L4

7.

How are Exceptions bound to handlers in C++? L3

Unit 5

1.

Explain L4

a) Common Lisp

b) Haskell

c) ML

2.

Discuss the applications of functional languages? L2

3.

Explain the difference between Imperative and functional languages? L4

4.

Outline the semantics of COND and LET? L2

Unit Wise Multiple Choice Questions for CRT & Competitive Examinations

Unit-1

1. Which of the following is true about system software.

a. The operating system and all programming support tools of a computer systems are collectively known as its

System Software.

b. The Operating System and the hardware tools of computer systems are called as system software.

c. The Operating System and the Macroinstruction interpreter collectively is known as system software.

d. System software is same as application software

2. Which of the following is the widely used programming language developed for Artificial Intelligence Application

a. ALGOL 60

b. LISP

c. FORTRAN

d. COBOL

3. Which is a scripting language developed by Netscape for use in both Web server and browsers. [01M01]

a. Java Script

b. HTML

c. AWK

d. PHP

4. Which of the following is the language developed to produce business reports.

a. RPG

b. GPSS

c. PHP

d. ALGOL

5. Which was the first language for scientific applications

a. ALGOL 60

b. FORTRA$

c. LISP

d. COBOL

6. Which was the first high-level language developed for business purpose. [01S02]

a. ALGOL 60

b. LISP

c. COBOL

d. FORTRAN

7. CGI stands for [01S03]

a. Common Gateway Interface

b. Computer Gateway Interface

d. Common Gateway interchange

8. The Unix Operating System is written almost entirely in _ _ _ _ __ _ Language

a. LISP

b. C

c. C++

d. Java

9. C was developed by _ _ _ _ _ _ _

a. Pascal

b. D.Ritchie

c. N.Writh d. A. Kay

10. List of Commands put in a file is called [01S06]

a. Script

b. Tag

c. Language d. Program

11. Languages designed around the prevalent computer architecture, called the von Neumann architecture are called as

a. Imperative Languages

b. Functional languages

c. Object - oriented Languages d. Improved Languages.

12. The first high level programming language to include pointer variables was _ _ _ _ _

a. Algol-60

b. Ada

c. PL/1

d. Fortran

13. The ability of a program to intercept run-time errors, take corrective measures and then continue execution is called

a. Error mechanics

b. Exception handling

c. Abstraction

d. Orthogonality

14. The first Language to provide even limited supported for data abstraction is [02M02]

a. Smalltalk

b. SIMULA67

c. Prolog++

15. Which of the following is true for abstraction

a. The ability to define and then use complicated structure in way that allow many of the details to be ignored

b. The process of hiding all low-level details from the user c. The ability to acquire properties of other class.

d. The ability of a program to intercept run-time errors.

Unit 2

1. A sentence generation is called a _ _ _ _ _ _ _ _ _ _ _ _ _

a. statement b. token

c. BNF

d. derivation

2. Which of the following is a device that can be used to generate the sentences of a language.

a. Sentence generator

b. Language generator

c. Program generator

d. Language recognizers

3. Which is correct about semantics

a. Rules for writing expressions, statements and program units

b. Meaning of the expression, statement and programs units

c. Protocol to be followed by statements

d. Conditions for writing expressions, statements and program units

4. Which of the following of a programming languages can be described by regular grammar

a. Tokens

b. Lexical units c. Lexemes

d. Syntax

5. Which is a language that is used to describe another language.

a. Terminal language

b. Meta language

c. Imperative language

d. Structural language

6. Which of the following is a natural notation for describing syntax

a. Context free grammar

b. Context sensitive grammars

c. Backus - $aur form

d. Regular grammar

7. Which are called the abstractions in a BNF description

a. $on terminals

b. Lexemes c. Tokens

d. Symbols

8. The syntax of a programming language is the form of its expressions, statements and _ _ _ _ _

a. program units

b. steps

c. functions

d. algorithms

9. For the instruction a = b/2 - 1 { a < 10 } is called as

a. Pre condition

b. Post condition

c. Weakest condition d. strong condition

10. For the instruction x = 2 * y - 3, {y < 0 } is called as

a. Pre condition

b. Post condition

c. Weakest condition d. strong condition

Unit-3

1. _ _ _ _ _ _ _ data type stores the data in BDC notation

a. float

b. double c. int

d. decimal

2. _ _ _ _ _ _ _ _ is one in which the range of possible values can be easily associated with the set of positive integers

a. variable b. data

c. ordinal type

d. constant

3. _ _ _ _ _ _ data type model real numbers, but only as approximations

a. float

b. char c. int

d. string

4. _ _ _ _ _ _ _ data type specifically available in a Language for business applications.

a. float

b. double c. int

d. decimal

5. The variables receive values at _ _ _ _ _ _ _ _ _ _ _ _ _ _

a. compile time

b. run time

c. language design time d. load time

6. The attributes of variables are determined at _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

a. compile time

b. run time

c. language design time d. load time

7. A _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ is a set of objects & a set of operations on those objects, which create, build-up, destroy, modify & pick apart instance of the objects

a. Data type

b. Data valued c. State space d. Environment

8. _ _ _ _ _ _ _ is not primitive data type,

a. float b. char c. int

d. string

9. _ _ _ _ _ _ _ _ _ data type store true or false notation

a. float

b. boolean

c. int

d. char

10. _ _ _ _ _ _ _ type stores values as sequences of characters

a. float

b. boolean c. int

d. string types

Unit- 4

1.Multiple selector statement in C is _ _ _ _ _

a. break

b. switch

c. go to

d. continue

2. _ _ _ _ _ _ _ is a two way selector

a. if

b. if else

c. for

d. while

3. In C Switch-Case statement the default expression type can be _ _ _ _ _ _ _ _ _

a. int

b. float

c. double d. char

4. The following is a Exit controlled loop

a. While

b. do-while

c. for

d. go to

5. In Pascal, after normal termination, loop variable is _ _ _ _ _ _ _ _ _ _

a. Undefined

b. assigned last value c. zero

d. one

6. _ _ _ _ _ _ _ _ _ _ language supports labeled iteration

a. C

b. C++

c. Java

d. Pascal

7. In FORTRAN 90, Loop parameters are evaluated _ _ _ _ _ _

a. only once

b. twice c. thrice

d. every time

8. In Ada 60, Loop parameters are evaluated _ _ _ _ _ _

a. only once b. Twice

c. Thrice

d. Everytime

9. The repeated execution of a statement or compound statement is accomplished by _ _ _ _ _

a. Iteration

b. Selection c. Condition d. Blocking

10. In Pascal, Loop parameters are evaluated _ _ _ _ _ _

a. Only once

b. Twice c. Thrice

d. Every time

University Question Papers

II B.TECH - II SEMESTER EXAMINATIONS, APRIL/MAY, 2011

PRINCIPLES OF PROGRAMMING LANGUAGES

(INFORMATION TECHNOLOGY)

Time: 3hours Max. Marks: 75

Answer any FIVE questions

All Questions Carry Equal Marks

- - -

1. How can knowledge of programming language characteristics benefits the whole computing Community? [15]

2.a) The two mathematical models of language description are generation and recognition. Describe how each can define the syntax of a programming language?

b) Develop an unambiguous grammar that describes the if statement. [8+7]

3.a) Explain all of the difference between subtypes and derived types.

b) Define union, free union and discriminated union? [8+7]

4.a) How does operand evaluation order interact with functional side effect ?

b) How does operand evaluation order interact with function side effects? [8+7]

5.a) Define Shallow and Deep binding for referencing environment of subprograms that Have been passed as parameters.

b) Write about Co routines. [8+7]

6.a) In what different places can the definition of a C++ member function appears?

b) What is a C++ namespace and what is its purpose? [8+7]

7. Explain the following with examples

a) Exception Handler

b) Disabling an exception

c) Continuation

d) Built-in Exception. [15]

8.a) What are the difference between CONS, LIST and APPENED?

b) Write a LISP function Fib(n) that computes nth Fibonacci number. [7+8]

********







- - -

1. What are some features of specific programming languages you know whose rationales are a mystery to you? [15]

2. Write a BNF description of the Boolean expressions of Java, including the three operators &&, || and ! and the relational expressions? [15]

3.a) What are the design issues for character string types?

b) What array initialization feature is available in Ada that is not available in other common imperative languages? [7+8]

4. Write text program in c++, java and c# to determine the scope of a variable declared in a for statement. Specifically the code must determine whether such variable is visible after the body of the for statement. [15]

5.a) What are the different models of parameter passing methods? How are they implemented? Give example for each.

b) What causes a C++ template function to be instantiated? [8+7]

6. Write an analysis of the similarities of and differences between java packages and C++ namespaces? [15]

7. What run-time errors or conditions, if any, an Pascal programs detect and handle? [15]

8. What scoping rule is used in

a) COMMON LISP

b) ML

c) Haskell. [15]

* * * * * *







- - -

1. Many languages distinguish between UPPER CASE and LOWER CASE letters in user-defined names. What are the pros and cons of this design decision? [15]

2.a) Describe the basic concept of denotational semantics?

b) What is the difference between synthesized and inherited attributes? [7+8]

3. What are all of the differences between the enumeration types of C++ and those of java? How does a decimal value waste memory space? [15]

4. Determine whether the narrowing explicit type conversions in two languages you know provide errors messages when a converted value loses its usefulness? [15]

5. What are the modes, the conceptual models of transfer, the advantages and disadvantages of pass by value, pass by result, pass by value - result and pass by - reference parameter- passing methods? [15]

6.a) What are the language design issues for abstract data types?

b) What are the disadvantages of designing an abstract data type to be a pointer? [7+8]

7. Write detailed compassion of the Exception Handling capabilities of C++ and those of JAVA? [15]

8. Define functional form and referential transparency? What data types were parts of the original LISP? [15]

********







- - -

1. Which produces faster Program execution, a Compiler (or) pure interpreter? What role does the symbol table play in a compiler? [15]

2.a) Describe the approach of using axiomatic semantics to convert the correctness of a given program?

b) Convert the following EBNF to BNF

S->A{bA}

A-> a[b]A [7+8]

3. What is the purpose of the ACTION, GOTO table of an LR parser? Explain With Example? [15]


5. Define static, fixed stack-dynamic, fixed heap-dynamic and heap-dynamic array. What are the advantages of each? [15]

6.a) What is the primary problem with using semaphores to provide synchronization?

b) Explain the difference between physical and logical concurrency? [8+7]

7. What is root class of all java exception classes? What is pattern class of most java user defined exception classes? [15]

8.a) Write a detail note on functions in ML.

b) Give comparison of Functional and Imperative Languages. [7+8]







- - -

1. How can knowledge of programming language characteristics benefits the whole computing Community? [15]

2.a) The two mathematical models of language description are generation and recognition. Describe how each can define the syntax of a programming language?

b) Develop an unambiguous grammar that describes the if statement. [8+7]

3.a) Explain all of the difference between subtypes and derived types.

b) Define union, free union and discriminated union? [8+7]

4.a) How does operand evaluation order interact with functional side effect ?

b) How does operand evaluation order interact with function side effects? [8+7]

5.a) Define Shallow and Deep binding for referencing environment of subprograms that Have been passed as parameters.

b) Write about Co routines. [8+7]

6.a) In what different places can the definition of a C++ member function appears?

b) What is a C++ namespace and what is its purpose? [8+7]

7. Explain the following with examples

a) Exception Handler

b) Disabling an exception

c) Continuation

d) Built-in Exception. [15]

8.a) What are the difference between CONS, LIST and APPENED?

b) Write a LISP function Fib(n) that computes nth Fibonacci number. [7+8]

********







- - -

1. What are some features of specific programming languages you know whose rationales are a mystery to you? [15]

2. Write a BNF description of the Boolean expressions of Java, including the three operators &&, || and ! and the relational expressions? [15]

3.a) What are the design issues for character string types?

b) What array initialization feature is available in Ada that is not available in other common imperative languages? [7+8]


5.a) What are the different models of parameter passing methods? How are they implemented? Give example for each.

b) What causes a C++ template function to be instantiated? [8+7]

6. Write an analysis of the similarities of and differences between java packages and C++ namespaces? [15]

7. What run-time errors or conditions, if any, an Pascal programs detect and handle? [15]

8. What scoping rule is used in

a) COMMON LISP

b) ML

c) Haskell. [15]

* * * * * *







- - -

1. Many languages distinguish between UPPER CASE and LOWER CASE letters in user-defined names. What are the pros and cons of this design decision? [15]

2.a) Describe the basic concept of denotational semantics?

b) What is the difference between synthesized and inherited attributes? [7+8]

3. What are all of the differences between the enumeration types of C++ and those of java? How does a decimal value waste memory space? [15]

4. Determine whether the narrowing explicit type conversions in two languages you know provide errors messages when a converted value loses its usefulness? [15]

5. What are the modes, the conceptual models of transfer, the advantages and disadvantages of pass by value, pass by result, pass by value - result and pass by - reference parameter- passing methods? [15]

6.a) What are the language design issues for abstract data types?

b) What are the disadvantages of designing an abstract data type to be a pointer? [7+8]

7. Write detailed compassion of the Exception Handling capabilities of C++ and those of JAVA? [15]

8. Define functional form and referential transparency? What data types were parts of the original LISP? [15]

********







- - -

1. Which produces faster Program execution, a Compiler (or) pure interpreter? What role does the symbol table play in a compiler? [15]

2.a) Describe the approach of using axiomatic semantics to convert the correctness of a given program?

b) Convert the following EBNF to BNF

S->A{bA}

A-> a[b]A [7+8]

3. What is the purpose of the ACTION, GOTO table of an LR parser? Explain With Example? [15]


5. Define static, fixed stack-dynamic, fixed heap-dynamic and heap-dynamic array. What are the advantages of each? [15]

6.a) What is the primary problem with using semaphores to provide synchronization?

b) Explain the difference between physical and logical concurrency? [8+7]

7. What is root class of all java exception classes? What is pattern class of most java user defined exception classes? [15]

8.a) Write a detail note on functions in ML.

b) Give comparison of Functional and Imperative Languages. [7+8]

B.Tech II Year - II Semester Examinations, December-January, 2011-2012



Time: 3 hours Max. Marks: 75

Answer any five questions

All questions carry equal marks

---

1.a) What are the advantages and disadvantages of Aliasing.

b) Readability and writability influence the reliability. Comment on it. [15]

2.a) Explain the general problem of describing syntax.

b) Consider the grammar E E+E

E E*E

E i

Using the expression 5+6*7, prove that the grammar is ambiguous. [15]

3.a) Discuss the design issues for pointer types.

b) Define the terms: coercion, type error, strong typing. [15]

4.a) Explain about mixed mode assignment.

b) Every counting loop can be built with a logical loop, but the reverse is not true. Substantiate this statement. [15]

5. What is meant by generic sub program? Explain the support provided by programming languages for generic subprograms. [15]

6.a) What advantages do monitors have over semaphores? Explain.

b) Explain why naming encapsulations are important for developing large programs.

[15]

7. Explain list processing in LISP using scheme functions. Use lucid examples in your explanation. [15]

8. What is exception? Discuss in detail the concept of exception propagation. [15]

********







- - -

1. Discuss language evaluation criteria and the characteristics that affect them. [15]

2.a) In what way do operational semantics and denotational semantics differ? Explain.

b) Describe the additional features of Extended BNF. [15]

3.a) Discuss the advantages and disadvantages of dynamic scoping.

b) What is a heterogeneous array? Discuss the design issues for arrays. [15]

4. Explain in detail the design issues for arithmetic expressions. [15]

5.a) Describe the three semantic models of parameter passing.

b) What is a parameter profile? Write about subprogram protocol. [15]

6.a) Compare the class entity access controls of C++ and Java.

b) Define race condition

c) What is the purpose of a task-ready queue? [15]

7.a) Explain the procedural abstraction in Python.

b) Discuss the fundamental of functional programming language. [15]

8. Give an overview of logic programming and discuss its applications. [15]

********







- - -

1. Explain various programming domains. What are your arguments for and against having a single language for all programming domains? [15]

2.a) Discuss the basic concept of Denotational semantics.

b) Show a parse tree and leftmost derivation for the statement: A=(A+B)*C

Given grammar is: =

A/B/C

+ /

* /

() / [15]

3.a) Compare and contrast Static binding with Dynamic binding.

b) Explain various user-defined ordinal types with examples. [15]

4.a) Discuss the problem of operand evaluation order and side effects along with possible solutions.

b) Describe user-located loop control mechanisms. [15]

5.a) Explain the general characteristics of subprograms.

b) What is a co-routine? How do they provide interleaved execution? [15]

6.a) What are the language design requirements for a languages that supports ADTs?

b) How is cooperation synchronization provided for Ada tasks? Explain. [15]

7. Discuss how scheme functions are used to solve the problems in simple list-processing with examples. [15]

8. Explain the basic elements of Prolog with illustrations. [15]

*********







- - -

1.a) List the potential benefits of studying concepts of programming language.

b) What are the important factors that influence the basic design of programming language? [15]

2. Describe briefly formal language generation mechanisms used to describe the syntax of programming languages. [15]

4.a) Define name type compatibility and structure type compatibility. What are the relative merits of these two?

b) Explain in detail implementation of pointer and reference types. [15]

4.a) Describe coercion in expressions.

b) Explain in detail Dijkstras guarded commands with examples. [15]

5. Explain variety of models that guide the implementation of the three basic parameter transmission modes. [15]

6.a) What dangers are avoided in Java by having implicit garbage collection, relative to C++?

b) Discuss the primary reason for all Java objects have a common ancestor.

c) What is a binary semaphore? Compare it with counting semaphore. [15]

7.a) Explain type inferencing in ML.

b) Discuss the key concepts of scripting language. [15]

8. Discuss various types of exceptions. Explain exception handler in Ada with suitable examples. [15]

B.Tech III-I Semester Examinations, December 2011


(COMPUTER SCIENCE AND ENGINEERING)




---

1. A programming language can be compiled or interpreted. Give relative advantages and disadvantages of compilation and interpretation. Give examples of compiled and interpreted languages. [16]

2. How do you describe the meaning of program using operational semantics? Explain with suitable examples and compare it with denotational semantics. [16]

3.a) Describe narrowing and widening conversion.

b) Explain the concept of late binding and early binding. [8+8]

4. Discuss different types of assignment statements. With lucid examples explain mixed mode assignment. [16]

5.a) Discuss the design issues of sub programs.

b) Write about overloaded subprograms.

c) What are coroutines? [16]

6.a) Discuss the Object oriented programming features supported in small talk.

b) What is meant by subprogram level concurrency? Explain. [8+8]

7. What is an exception? Explain exception propagation and handling in C++. [16]

8.a) Write about functions in ML and Haskell.

b) Discuss the data types supported in Python. [8+8]

--ooOoo-- RRCode No: RR310505 SET-1







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--ooOoo-- RRCode No: RR310505 SET-2







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--







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Tutorial Sheet

Unit-I

Topics Revised

Date:

Quick Test Topics

Date:

Case Study Discussed

Date:

Unit-II

Topics Revised

Date:

Quick Test Topics

Date:


Date:

Unit-III

Topics Revised

Date:

Quick Test Topics

Date:


Date:

Unit-IV

Topics Revised

Date:

Quick Test Topics

Date:


Date:

Unit-V

Topics Revised

Date:

Quick Test Topics

Date:


Date:

TOPICS BEYOND SYLLABUS

Unit 1

1.

2.

3.

4.

Unit 2

1.

2.

3.

4.

Unit 3

1.

2.

3.

4.

Unit 4

1.

2.

3.

4.

Unit 5

1.

2.

3.

4.

5.

ASSESMENT OF LEARNING OBJECTIVES AND OUT COMES: DIRECT

Blooms Taxonomy:

LEVEL 1

REMEMBERING

Exhibit memory of previously learned material by recalling facts, terms, basic concepts, and answers

LEVEL 2

UNDERSTANDING

Demonstrate understanding of facts and ideas by organizing, comparing, translating, interpreting, giving descriptions, and stating main ideas.

LEVEL 3

APPLYING

Solve problems to new situations by applying acquired knowledge, facts, techniques and rules in a different way

LEVEL 4

ANALYZING

Examine and break information into parts by identifying motives or causes. Make inferences and find evidence to support generalizations.

LEVEL 5

EVALUATING

Present and defend opinions by making judgments about information, validity of ideas, or quality of work based on a set of criteria.

LEVEL 6

CREATING

Compile information together in a different way by combining elements in a new pattern or proposing alternative solutions.

S.No.

Hall Ticket

Number

I-Internal

Marks

Assignment

Marks

Remarks &

Blooms Taxonomy Assessment

II-Internal

Marks

Assignment

Marks

Remarks &


Avg.

Marks

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

ASSESMENT OF LEARNING OBJECTIVES AND OUT COMES: INDIRECT

Blooms Taxonomy:

LEVEL 1

REMEMBERING

Exhibit memory of previously learned material by recalling facts, terms, basic concepts, and answers

LEVEL 2

UNDERSTANDING

Demonstrate understanding of facts and ideas by organizing, comparing, translating, interpreting, giving descriptions, and stating main ideas.

LEVEL 3

APPLYING

Solve problems to new situations by applying acquired knowledge, facts, techniques and rules in a different way

LEVEL 4

ANALYZING

Examine and break information into parts by identifying motives or causes. Make inferences and find evidence to support generalizations.

LEVEL 5

EVALUATING

Present and defend opinions by making judgments about information, validity of ideas, or quality of work based on a set of criteria.

LEVEL 6

CREATING

Compile information together in a different way by combining elements in a new pattern or proposing alternative solutions.

S.N0

Criteria

LEVEL ( Level : 5-Excellent Level :4-Very Good Level :3-Good Level :2-Satisfactory Level : 1-Poor )

1

Oral

Communication

5

Student speaks in phase with the given topic confidently using Audio-Visual aids. Vocabulary is exceptional

4

Student speaking with proper planning, fair usage of Audio-Visual aids. Vocabulary is good

3

Student speaking without proper planning, fair usage of Audio-Visual aids. Vocabulary is not good

2

Student speaks in phase but no synchronization among the talk and Visual Aids.

1

Student speaks vaguely not in phase with the given topic.

2

Writing Skills

5

Proper structuring of the document with relevant subtitles, readability of document is high with correct use of grammar. Work is genuine and not published anywhere else.

4

Information gathered is relevant to the given task. sentences were framed properly with correct use of grammar.

3

Information gathered is relevant to the given task. sentences were framed properly with inappropriate use of grammar

2

Information is gathered without continuity of topic, sentences were not framed properly. Few topics are copied from other documents

1

Information gathered was not relevant to the given task. Content is copied from other documents

3

Social and Ethical Awareness

5

Student identifies most potential ethical or societal issues and provides solutions for them discussing with peers

4

Student identifies most potential ethical or societal issues and provides partial solutions for them discussing with peers

3

Student identifies the societal and ethical issues but tries to provide solutions for them discussing with peers

2

Student identifies the societal and ethical issues but fails to provide any solutions discussing with peers

1

Student makes no attempt in identifying the societal and ethical issues

4

Content Knowledge

5

Student uses appropriate methods, techniques to model and solve the problem accurately

4.

Student uses appropriate methods, techniques to model and solve the problem partially.

3

Student uses appropriate methods to model the problem but attempts to solve the problem

2

Student tries to model the problem and fails to solve the problem

1

Student fails to model the problem and also fails to solve the problem

5

Student Participation

5

Listens carefully to the class and answer the questions confidently

4

Listens carefully to the class and tries to answer questions confidently.

3

Listens carefully to the lecture and attempts to answer the questions

2

Student listens to the class but doesnt attempts to answer the questions

1

Student neither listens to the class nor attempts to answer the questions

6

Technical and analytical Skills

5

The program structure is well organized with appropriate use of technologies and methodology. Code is easy to read and well documented. Student is able to implement the algorithm producing accurate results

4

Program structure is well organized with appropriate use of technologies and methodology. Code is easy to read and not properly documented. Student is able to implement the algorithm providing accurate results.

3

Program structure is well organized with appropriate use of technologies and methodology. Code is quite difficult to read and not properly documented. Student is able to implement the algorithm providing accurate results.

2

Program structure is well organized with usage of appropriate technologies and methodology. Code is difficult to read and not documented properly and not able to execute the program

1

Program structure is not well organized with mistakes in usage of appropriate technologies and methodology. Code is difficult to read and student is not able to execute the program

7

Practical Knowledge

5

Independently able to write programs for any given context to strengthen the concepts covered in theory

4

Independently able to write programs to strengthen the concepts covered in theory

3

Independently able to write programs and able to strengthen the concepts learned in theory

2

Not able to write programs but able to strengthen the concepts learned in theory.

1

Not able to write programs and not able to strengthen the concepts learned in theory

8

Understanding of Engineering core

5

Student uses appropriate methods, techniques to model and solve the problem accurately in the context of multidisciplinary projects

4

Student tries to model the problem and solve the problem in the context of multidisciplinary projects

3

Student tries to model the problem and attempts to solve the problem in the context

of multidisciplinary projects.

2

Student tries to model the problem but fails to solve the problem in the context

of multidisciplinary projects.

1

Student fails to model the problem and also fails to solve the problem in the context

of multidisciplinary projects

CSP Rubric Name & Number:

S.No.

Hall Ticket Number

Rubric Assessment


Remarks

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

Remedial Classes:

Unit Number

Date Conducted

Topics Revised

Unit-I

Unit-II

Unit-III

Unit-IV

Unit-V

Unit-VI

Unit-VII

Unit-VIII

Add-on Programmes:

1 To conduct lab

Guest Lectures:

1.

2.

3.

4.

Unit Wise lecture Notes:

UNIT-I

Preliminaries Concepts

Topics

1. Reasons for Studying Concepts of Programming Languages

2. Programming Domains

3. Language Evaluation Criteria

4. Influences on Language Design

5. Language Categories

6. Language Design Trade-Offs

7. Implementation Methods

8. Programming Environments

`

Background

Frankly, we didnt have the vaguest idea how the thing [FORTRAN language and compiler] would work out in detail. We struck out simply to optimize the object program, the running time, because most people at that time believed you couldnt do that kind of thing. They believed that machined-coded programs would be so inefficient that it would be impractical for many applications.

-John Backus

Unexpected successes are common the browser is another example of an unexpected success

1.1 Reasons for Studying Concepts of Programming Languages

Increased ability to express ideas

Improved background for choosing appropriate languages

Increased ability to learn new languages

Better understanding of significance of implementation

Overall advancement of computing

1.2 Programming Domains

Scientific applications

Large number of floating point computations

Fortran

Business applications

Produce reports, use decimal numbers and characters

COBOL

Artificial intelligence

Symbols rather than numbers manipulated

LISP

Systems programming

Need efficiency because of continuous use

C

Web Software

Eclectic collection of languages: markup (e.g., XHTML), scripting (e.g., PHP), general-purpose (e.g., Java)

1.3 Language Evaluation Criteria

Readability: the ease with which programs can be read and understood

Writability: the ease with which a language can be used to create programs

Reliability: conformance to specifications (i.e., performs to its specifications)

Cost: the ultimate total cost

Evaluation Criteria: Readability

Overall simplicity

A manageable set of features and constructs

Few feature multiplicity (means of doing the same operation)

Minimal operator overloading

Orthogonality

A relatively small set of primitive constructs can be combined in a relatively small number of ways

Every possible combination is legal

Control statements

The presence of well-known control structures (e.g., while statement)

Data types and structures

The presence of adequate facilities for defining data structures

Syntax considerations

Identifier forms: flexible composition

Special words and methods of forming compound statements

Form and meaning: self-descriptive constructs, meaningful keywords

Evaluation Criteria: Writability

Simplicity and orthogonality

Few constructs, a small number of primitives, a small set of rules for combining them

Support for abstraction

The ability to define and use complex structures or operations in ways that allow details to be ignored

Expressivity

A set of relatively convenient ways of specifying operations

Example: the inclusion of for statement in many modern languages

Evaluation Criteria: Reliability

Type checking

Testing for type errors

Exception handling

Intercept run-time errors and take corrective measures

Aliasing

Presence of two or more distinct referencing methods for the same memory location

Evaluation Criteria: Cost

Training programmers to use language

Writing programs (closeness to particular applications)

Compiling programs

Executing programs

Language implementation system: availability of free compilers

Reliability: poor reliability leads to high costs

Maintaining programs

Evaluation Criteria: Others

Portability

The ease with which programs can be moved from one implementation to another

Generality

The applicability to a wide range of applications

Well-definedness

The completeness and precision of the languages official definition

1.4 Influences on Language Design

Computer Architecture

Languages are developed around the prevalent computer architecture, known as the von Neumann architecture

Programming Methodologies

New software development methodologies (e.g., object-oriented software development) led to new programming paradigms and by extension, new programming languages

Computer Architecture Influence

Well-known computer architecture: Von Neumann

Imperative languages, most dominant, because of von Neumann computers

Data and programs stored in memory

Memory is separate from CPU

Instructions and data are piped from memory to CPU

Basis for imperative languages

Variables model memory cells

Assignment statements model piping

Iteration is efficient

The von Neumann Architecture

Programming Methodologies Influences

1950s and early 1960s: Simple applications; worry about machine efficiency

Late 1960s: People efficiency became important; readability, better control structures

structured programming

top-down design and step-wise refinement

Late 1970s: Process-oriented to data-oriented

data abstraction

Middle 1980s: Object-oriented programming

Data abstraction + inheritance + polymorphism

1.5 Language Categories

Imperative

Central features are variables, assignment statements, and iteration

Examples: C, Pascal

Functional

Main means of making computations is by applying functions to given parameters

Examples: LISP, Scheme

Logic

Rule-based (rules are specified in no particular order)

Example: Prolog

Object-oriented

Data abstraction, inheritance, late binding

Examples: Java, C++

Markup

New; not a programming per se, but used to specify the layout of information in Web documents

Examples: XHTML, XML

1.6 Language Design Trade-Offs

Reliability vs. cost of execution

Conflicting criteria

Example: Java demands all references to array elements be checked for proper indexing but that leads to increased execution costs

Readability vs. writability

Another conflicting criteria

Example: APL provides many powerful operators (and a large number of new symbols), allowing complex computations to be written in a compact program but at the cost of poor readability

Writability (flexibility) vs. reliability

Another conflicting criteria

Example: C++ pointers are powerful and very flexible but not reliably used

1.7 Implementation Methods

Compilation

Programs are translated into machine language

Pure Interpretation

Programs are interpreted by another program known as an interpreter

Hybrid Implementation Systems

A compromise between compilers and pure interpreters

Layered View of Computer

The operating system and language implementation are layered over Machine interface of a computer

Compilation

Translate high-level program (source language) into machine code (machine language)

Slow translation, fast execution

Compilation process has several phases:

lexical analysis: converts characters in the source program into lexical units

syntax analysis: transforms lexical units into parse trees which represent the syntactic structure of program

Semantics analysis: generate intermediate code

code generation: machine code is generated

The Compilation Process

Additional Compilation Terminologies

Load module (executable image): the user and system code together

Linking and loading: the process of collecting system program and linking them to user program

Execution of Machine Code

Fetch-execute-cycle (on a von Neumann architecture)

initialize the program counter

repeat forever

fetch the instruction pointed by the counter

increment the counter

decode the instruction

execute the instruction

end repeat

Von Neumann Bottleneck

Connection speed between a computers memory and its processor determines the speed of a computer

Program instructions often can be executed a lot faster than the above connection speed; the connection speed thus results in a bottleneck

Known as von Neumann bottleneck; it is the primary limiting factor in the speed of computers

Pure Interpretation

No translation

Easier implementation of programs (run-time errors can easily and immediately displayed)

Slower execution (10 to 100 times slower than compiled programs)

Often requires more space

Becoming rare on high-level languages

Significant comeback with some Web scripting languages (e.g., JavaScript)

Hybrid Implementation Systems

A compromise between compilers and pure interpreters

A high-level language program is translated to an intermediate language that allows easy interpretation

Faster than pure interpretation

Examples

Perl programs are partially compiled to detect errors before interpretation

Initial implementations of Java were hybrid; the intermediate form, byte code, provides portability to any machine that has a byte code interpreter and a run-time system (together, these are called Java Virtual Machine)

Just-in-Time Implementation Systems

Initially translate programs to an intermediate language

Then compile intermediate language into machine code

Machine code version is kept for subsequent calls

JIT systems are widely used for Java programs

.NET languages are implemented with a JIT system

Preprocessors

Preprocessor macros (instructions) are commonly used to specify that code from another file is to be included

A preprocessor processes a program immediately before the program is compiled to expand embedded preprocessor macros

A well-known example: C preprocessor

expands #include, #define, and similar macros

Describing Syntax and Semantics

Topics

Introduction

The General Problem of Describing Syntax

Formal Methods of Describing Syntax

Attribute Grammars

Describing the Meanings of Programs: Dynamic Semantics

2.1 Introduction

Syntax: the form or structure of the expressions, statements, and program units

Semantics: the meaning of the expressions, statements, and program units

Syntax and semantics provide a languages definition

o Users of a language definition

Other language designers

Implementers

Programmers (the users of the language)

2.2 The General Problem of Describing Syntax: Terminology

A sentence is a string of characters over some alphabet

A language is a set of sentences

A lexeme is the lowest level syntactic unit of a language (e.g., *, sum, begin)

A token is a category of lexemes (e.g., identifier)

Formal Definition of Languages

Recognizers

A recognition device reads input strings of the language and decides whether the input strings belong to the language

Example: syntax analysis part of a compiler

Detailed discussion in Chapter 4

Generators

A device that generates sentences of a language

One can determine if the syntax of a particular sentence is correct by comparing it to the structure of the generator

2.3 Formal Methods of Describing Syntax

Backus-Naur Form and Context-Free Grammars

Most widely known method for describing programming language syntax

Extended BNF

Improves readability and writability of BNF

Grammars and Recognizers

BNF and Context-Free Grammars

Context-Free Grammars

Developed by Noam Chomsky in the mid-1950s

Language generators, meant to describe the syntax of natural languages

Define a class of languages called context-free languages

Backus-Naur Form (BNF)

Backus-Naur Form (1959)

Invented by John Backus to describe Algol 58

BNF is equivalent to context-free grammars

BNF is ametalanguage used to describe another language

In BNF, abstractions are used to represent classes of syntactic structures--they act like syntactic variables (also called nonterminal symbols)

BNF Fundamentals

Non-terminals: BNF abstractions

Terminals: lexemes and tokens

Grammar: a collection of rules

Examples of BNF rules:

identifier | identifer,

if then

BNF Rules

A rule has a left-hand side (LHS) and a right-hand side (RHS), and consists of terminal and nonterminal symbols

A grammar is a finite nonempty set of rules

An abstraction (or nonterminal symbol) can have more than one RHS

| begin end

Describing Lists

Syntactic lists are described using recursion

ident

| ident,

A derivation is a repeated application of rules, starting with the start symbol and ending with a sentence (all terminal symbols)

An Example Grammar

| ;

=

a | b | c | d

+ | -

| const

An example derivation

=> =>

= => a =

a = +

a = +

a = b +

a = b + const

Derivation

Every string of symbols in the derivation is a sentential form

A sentence is a sentential form that has only terminal symbols

A leftmost derivation is one in which the leftmost nonterminal in each sentential form is the one that is expanded

A derivation may be neither leftmost nor rightmost

Parse Tree

A hierarchical representation of a derivation

Ambiguity in Grammars

A grammar is ambiguous iff it generates a sentential form that has two or more distinct parse trees

An Ambiguous Expression Grammar

An Unambiguous Expression Grammar

If we use the parse tree to indicate precedence levels of the operators, we cannot have ambiguity

- |

/ const| const

Associativity of Operators

Operator associativity can also be indicated by a grammar

-> + | const (ambiguous)

-> + const | const (unambiguous)

Extended BNF

Optional parts are placed in brackets ([ ])

-> ident [()]

Alternative parts of RHSs are placed inside parentheses and separated via vertical bars

(+|-) const

Repetitions (0 or more) are placed inside braces ({ })

letter {letter|digit}

BNF and EBNF

BNF

+

| -

|

*

| /

|

EBNF

{(+ | -) }

{(* | /) }

2.4 Attribute Grammars

Context-free grammars (CFGs) cannot describe all of the syntax of programming languages

Additions to CFGs to carry some semantic info along parse trees

Primary value of attribute grammars (AGs):

Static semantics specification

Compiler design (static semantics checking)

Attribute Grammars : Definition

An attribute grammar is a context-free grammar G = (S, N, T, P) with the G.

following additions:

For each grammar symbol x there is a set A(x) of attribute values

Each rule has a set of functions that define certain attributes of the nonterminals in the rule

Each rule has a (possibly empty) set of predicates to check for attribute consistency

Let X0 X1 ... Xn be a rule

Functions of the form S(X0) = f(A(X1), ... , A(Xn)) define synthesized attributes

Functions of the form I(Xj) = f(A(X0), ... , A(Xn)), for i + |

A | B | C

actual_type: synthesized for and

expected_type: inherited for

Syntax rule: [1] + [2]

Semantic rules:

.actual_type [1].actual_type

Predicate:

[1].actual_type == [2].actual_type

.expected_type == .actual_type

Syntax rule: id

Semantic rule:

.actual_type lookup (.string)

How are attribute values computed?

If all attributes were inherited, the tree could be decorated in top-down order.

If all attributes were synthesized, the tree could be decorated in bottom-up order.

In many cases, both kinds of attributes are used, and it is some combination of top-down and bottom-up that must be used.

.expected_type inherited from parent

[1].actual_type lookup (A)

[2].actual_type lookup (B)

[1].actual_type =? [2].actual_type

.actual_type [1].actual_type

.actual_type =? .expected_type

2.5 Semantics

There is no single widely acceptable notation or formalism for describing semantics

Operational Semantics

Describe the meaning of a program by executing its statements on a machine, either simulated or actual. The change in the state of the machine (memory, registers, etc.) defines the meaning of the statement

To use operational semantics for a high-level language, a virtual machine is needed

A hardware pure interpreter would be too expensive

A software pure interpreter also has problems:

The detailed characteristics of the particular computer would make actions difficult to understand

Such a semantic definition would be machine- dependent

Operational Semantics

A better alternative: A complete computer simulation

The process:

Build a translator (translates source code to the machine code of an idealized computer)

Build a simulator for the idealized computer

valuation of operational semantics:

Good if used informally (language manuals, etc.)

Extremely complex if used formally (e.g., VDL), it was used for describing semantics of PL/I.

Axiomatic Semantics

Based on formal logic (predicate calculus)

Original purpose: formal program verification

Approach: Define axioms or inference rules for each statement type in the language (to allow transformations of expressions to other expressions)

The expressions are called assertions

Axiomatic Semantics

An assertion before a statement (a precondition) states the relationships and constraints among variables that are true at that point in execution

An assertion following a statement is a postcondition

A weakest precondition is the least restrictive precondition that will guarantee the postcondition

Pre-post form: {P} statement {Q}

An example: a = b + 1 {a > 1}

One possible precondition: {b > 10}

Weakest precondition: {b > 0}

Program proof process: The postcondition for the whole program is the desired result. Work back through the program to the first statement. If the precondition on the first statement is the same as the program spec, the program is correct.

An axiom for assignment statements (x = E):

{Qx->E} x = E {Q}

An inference rule for sequences

For a sequence S1;S2:

{P1} S1 {P2}

{P2} S2 {P3}

An inference rule for logical pretest loops

For the loop construct:

{P} while B do S end {Q}

Characteristics of the loop invariant

I must meet the following conditions:

P => I (the loop invariant must be true initially)

{I} B {I} (evaluation of the Boolean must not change the validity of I)

{I and B} S {I} (I is not changed by executing the body of the loop)

(I and (not B)) => Q (if I is true and B is false, Q is implied)

The loop terminates (this can be difficult to prove)

The loop invariant I is a weakened version of the loop postcondition, and it is also a precondition.

I must be weak enough to be satisfied prior to the beginning of the loop, but when combined with the loop exit condition, it must be strong enough to force the truth of the postcondition

Evaluation of axiomatic semantics:

Developing axioms or inference rules for all of the statements in a language is difficult It is a good tool for correctness proofs, and an excellent framework for reasoning about programs, but it is not as useful for language users and compiler writers

Its usefulness in describing the meaning of a programming language is limited for language users or compiler writers

Denotational Semantics

Based on recursive function theory

The most abstract semantics description method

Originally developed by Scott and Strachey (1970)

The process of building a denotational spec for a language (not necessarily easy):

Define a mathematical object for each language entity

Define a function that maps instances of the language entities onto instances of the corresponding mathematical objects

The meaning of language constructs are defined by only the values of the program's variables

The difference between denotational and operational semantics: In operational semantics, the state changes are defined by coded algorithms; in denotational semantics, they are defined by rigorous mathematical functions

The state of a program is the values of all its current variables

s = {, , , }

Let VARMAP be a function that, when given a variable name and a state, returns the current value of the variable

VARMAP(ij, s) = vj

Decimal Numbers

The following denotational semantics description maps decimal numbers as strings of symbols into numeric values

0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

| (0 | 1 | 2 | 3 | 4 |

5 | 6 | 7 | 8 | 9)

Mdec('0') = 0, Mdec ('1') = 1, , Mdec ('9') = 9

Mdec ( '0') = 10 * Mdec ()

Mdec ( '1) = 10 * Mdec () + 1

Mdec ( '9') = 10 * Mdec () + 9

Expressions

Map expressions onto Z {error}

We assume expressions are decimal numbers, variables, or binary expressions having one arithmetic operator and two operands, each of which can be an expression

Me(, s) =

case of

=> Mdec(, s)

=>

if VARMAP(, s) == undef

then error

else VARMAP(, s)

=>

if (Me(., s) == undef

OR Me(., s) =

undef)

then error

else

if (. == + then

Me(., s) +

Me(., s)

else Me(., s) *

Me(., s)

...

Assignment Statements

Maps state sets to state sets

Ma(x := E, s) =

if Me(E, s) == error

then error

else s = {,,...,},

where for j = 1, 2, ..., n,

vj = VARMAP(ij, s) if ij x

= Me(E, s) if ij == x

Logical Pretest Loops

o Maps state sets to state sets

Ml(while B do L, s) =

if Mb(B, s) == undef

then error

else if Mb(B, s) == false

then s

else if Msl(L, s) == error

then error

else Ml(while B do L, Msl(L, s))

The meaning of the loop is the value of the program variables after the statements in th

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