Programming Language and Compiler Design Session

8/14/2019 Programming Language and Compiler Design Session

1/33

Programming Language andCompiler Design

L.Ramkumar


2/33

What Is A Programming Language?

A tool for instructing machines A means of communicating between

programmers

A vehicle for expressing high-level designs A notation for algorithms A way of expressing relationships between

concepts

A tool for experimentation A means for controlling computerized

devices


3/33

Levels

Gross distinction betweenprogramming language

Based on readability Based on independence

Based on purpose (specific general)


4/33

Levels

Machine levellanguage

Assembly levellanguage

High-level language (3GL) Sometimes 4GL - fourth generation

language


5/33

Machine Level

00000010101111001010

00000010101111001000

00000011001110101000 Programs in machine language are

usually unintelligible at the lowest level,the most detailed level, since they

consists only of 0s and 1s


6/33

Assembly Language

Assembly language is a variant ofmachine language in which namesand symbols take the place of theactual codes for machine operations,values, and storage locations, makingindividual instructions more readable.


7/33

Individual instructions in assemblylanguage are readable, but limitationsof the underlying machine can lead toconvoluted programs.


8/33

Basic Concepts of a RAM machine

Memory: addresses, contents

Program: instructions

Input/output: (files)


9/33

Program A random access machine

1. M[0] :=02. Read (M[1])3. If M[1] 0 then goto 54. Goto 75. M[3] := M[0] M[1]6. If M[3] 0 then goto 167. Writeln (M[1])8. Read (M[2])9. M[3] := M[2] M[1]10. If M[3] 0 then goto 1211. Goto 1412. M[3] := M[1] M[2]

13. If M[3] 0 then goto 814. M[1] := M[2] M[0]15. Goto 316. halt

Control

Input

0 1Memory

Output


10/33

High Level

Readable familiar notations

Machine independence

Availability of program libraries Consistency check (check data types


11/33


12/33

Problems of Scale

Changes are easy to make Isolated program fragments can be

understood

BUT one small bug can lead to disaster Read the NOT story about Mariner rockets

(Refer http://en.wikipedia.org/wiki/Mariner_1)

Notice how the chairman does not

understand that a small problem can leadto devastating result and why it was notcaught


13/33

Bugs

Programming testing can be used toshow the presence of bugs, but nevertheir absence! - Dijkstra

Programming Languages can help

Readable and understandable

Organize such that parts can beunderstood.


14/33

Role of Programming Languages

Art (science) of programming isorganizing complexity

Must organize in such a way that our

limited powers are sufficient toguarantee that the computation willestablish the desired effect

(Dijkstra - structured programming,sometimes referred to as goto-lessprogramming)


15/33

Programming Paradigms

Imperative Programming

Functional Programming

Object Oriented Programming Logic Programming


16/33


17/33

Pascal was designed as a teachinglanguage.

C was created in 1972 by DennisRitche as an implementationlanguage associated with UNIXoperating System

In 1973 UNIX Operating System wasrewritten in C.


18/33

Functional Programming

The basic concepts of functional languagesoriginated with Lisp, a language designed in1958 for applications in artificial

intelligence. Lisp is designed primarily for symbolic data

processing.

Used for symbolic calculation in differential

and integral calculus, electrical circuittheory, mathematical logic, game playingand other field of artificial intelligence.


19/33

Object Oriented Programming

Object Oriented Programming owesmuch to Simulas origin in simulation.

The key concept from Simula is thatof a class of objects.

C++ and Smalltalk are popularlanguages for Object Oriented

Programming.


20/33

C++ was designed to bring thebenefits of objects to imperativeprogramming in C.

Smalltalk was designed as part of apersonal computing environment.

It is an interactive system with a

graphical user interface.


21/33

Logic Programming

Prolog was developed in 1972.

Prolog uses a specialized form of

logical reasoning to answer queries.


22/33

%% Demo coming from http://clwww.essex.ac.uk/course/LG519/2-facts/index_18.html %% %% Please load this file into SWI-Prolog %% %% Sam's likes and dislikes in food %%

%% Considering the following will give some practice %% in thinking about backtracking. %% ?- likes(sam,dahl). %% ?- likes(sam,chop_suey). %% ?- likes(sam,pizza). %% ?- likes(sam,chips). %% ?- likes(sam,curry).

likes(sam,Food) :- indian(Food), mild(Food). likes(sam,Food) :- chinese(Food). likes(sam,Food) :- italian(Food). likes(sam,chips).

indian(curry). indian(dahl). indian(tandoori). indian(kurma).

mild(dahl). mild(tandoori). mild(kurma).

chinese(chow_mein). chinese(chop_suey). chinese(sweet_and_sour).

italian(pizza). italian(spaghetti).


23/33

Choice of Language

The choice of programming languagedepends in part on the programmingto be done, and in part on externalfactors, such as availability, supportand training


24/33

Language Implementation

Compiler - source code it translatedinto machine code (all at once) Source code is portable compiled code

is NOT portable Interpreter - machine is brought up

to the language (one statement at atime Source code is portable; executable on

any computer (that has an interpreterfor that language)


25/33


26/33

Compiled C

Source

code

in C

Pre-

procces

sor compiler

Linker

or

assembler

Machine

code (exe)

LoaderMachine

codes

.o

files

Pre

processed

code

Source code language is brought downto the machine language of that

specific computer


27/33

Interpreted Code

Each instruction is interpreted bymachine interpreter

Does not produce object code

Machine is brought up to a virtual machine that executes the

source code


28/33

Comparisons

Compilation more efficient

Interpreted more flexible

Mixed-mode good for distributedenvironments (e.g. Webclient/server)


29/33

Major Parts of Compilers

There are two major parts of a compiler: Analysisand Synthesis

In analysis phase, an intermediate representation is

created from the given source program. Lexical Analyzer, Syntax Analyzer and Semantic

Analyzer are the parts of this phase. In synthesis phase, the equivalent target program is

created from this intermediate representation.

Intermediate Code Generator, Code Generator, andCode Optimizer are the parts of this phase.


30/33

Other Applications In addition to the development of a compiler, the

techniques used in compiler design can be applicableto many problems in computer science. Techniques used in a lexical analyzer can be used in

text editors, information retrieval system, and

pattern recognition programs. Techniques used in a parser can be used in a query

processing system such as SQL. Many software having a complex front-end may need

techniques used in compiler design. A symbolic equation solver which takes an equation as

input. That program should parse the given inputequation. Most of the techniques used in compiler design can

be used in Natural Language Processing (NLP)systems.


31/33

Phases of A Compiler

Each phase transforms the source

program from one representationintoanother representation.

They communicate with errorhandlers.

They communicate with the symboltable.

Lexical

Analyzer

Semantic

Analyzer

Syntax

Analyzer

Intermediate

Code Generator

Code

Optimizer

Code

Generator

Target

ProgramSource

Program


32/33

Lex and Yacc

Lex and yacc are tools used togenerate lexical analyzers andparsers.


33/33

Documents

Programming Language and Compiler Design Session