isbn 0-321-19362-8 lecture 01 preliminaries. copyright © 2004 pearson addison-wesley. all rights...
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ISBN 0-321-19362-8
Lecture 01
Preliminaries
Copyright © 2004 Pearson Addison-Wesley. All rights reserved. 1-2
Lecture 01 Topics
• Motivation• Programming Domains• Language Evaluation Criteria• Influences on Language Design• Language Categories• Language Design Trade-Offs• Implementation Methods• Programming Environments
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Motivation: Why Study Programming Languages?• Increased ability to express ideas• Improved background for choosing
appropriate languages• Greater ability to learn new languages• Understand significance of
implementation• Ability to design new languages• Overall advancement of computing
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Programming Domains• Scientific applications
– Large number of floating point computations
• Business applications– Produce reports, use decimal numbers and characters
• Artificial intelligence– Symbols rather than numbers manipulated
• Systems programming– Need efficiency because of continuous use
• Scripting languages– Put a list of commands in a file to be executed
• Special-purpose languages– Simulation
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Language Evaluation Criteria
• Readability– The most important criterium– Factors:
• Overall simplicity– Too many features is bad– Multiplicity of features is bad
• Orthogonality– A relatively small set of primitive constructs can be
combined in a relatively small number of ways – Every possible combination is legal– Meaning is context independent– Lack of orthogonality leads to exceptions to rules– Makes the language easy to learn and read
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Language Evaluation Criteria
– Readability factors (continued)• Control statements
– goto
• Defining data types and structures– True vs 1, record vs array
• Syntax considerations– Identifier forms– Special words– Form and meaning
» Meaning should directly follows syntax » static
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Language Evaluation Criteria
• Writability– Factors:
• Simplicity and orthogonality• Support for abstraction
– Program and data abstraction
• Expressivity
• Reliability– Factors:
• Type checking• Exception handling• Aliasing• Readability and writability
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Language Evaluation Criteria
• Cost– Training programmers to use language– Writing programs– Compiling programs– Executing programs– Language implementation system– Reliability– Maintaining programs
• Others: portability, generality, well-definedness
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Influences on Language Design
• Computer architecture: Von Neumann • We use imperative languages, at least
in part, because we use von Neumann machines– Data and programs stored in same
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
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Von Neumann Architecture
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Influences on Language Design• Programming methodologies
– 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
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Language Categories
• Imperative– Central features are variables,
assignment statements, and iteration– C, Pascal
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Language Categories• Factorial in C
#include <stdio.h>long factorial (int n);
void main(void){
printf("The factorial of %d is %d\n", 10, factorial (10));
}
long factorial (int n){
int i;long product =1;for(i = n; i>0); i--)
product = product *i;return product;
}
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Language Categories
• Functional– Main means of making computations is
by applying functions to given parameters
– LISP, Scheme– Factorial in Lisp
=> (defun factorial (n)
(cond ((= n 0) 1)
(t (* n (factorial (- n 1))))
))
=> (factorial 10)
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Language Categories
• Object-oriented– Encapsulate data objects with
processing– Inheritance and dynamic type binding– Grew out of imperative languages– C++, Java
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Language Categories• Factorial in Java
import java.io.*;public class Factorial{ private long product = 1;
private int n;
public Factorial(int k){ n = k;}
void run (void){ int i;
for (i = n; n > 0; i--)product = product *i;
System.out.println("The factorial of " + n + "is " + product);}
public static void main (void){ Factorial fact10 = new Factorial(10);
fact10.run();}
}
=> java Factorial
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Language Categories
• Logic– Rule-based knowledge base– Rules are specified in no special order– Prolog– Factorial in Prolog
factorial(0, 1).
factorial(N, F) :- N>0, factorial(N1, F1), N is N1 + 1, F is F1 * N.
=>?factorial(10, what).
=> True.
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Language Design Trade-Offs
• Criteria in conflict– Reliability vs. cost of execution– Readability vs. writability– Flexibility vs. safety
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Layered View of Computer
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Implementation Methods
• Compilation– Translate high-level program to
machine code– Slow translation– Fast execution
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Compilation Process
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Implementation Methods
• Pure interpretation– No translation– Slow execution– Becoming rare– Used most in scripting languages
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Pure Interpretation
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Implementation Methods
• Hybrid implementation systems– Small translation cost– Medium execution speed
• Two-level compilation– Intermediate code interpretation
replaced by JIT (Just In Time) compilation
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Hybrid Implementation System
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Programming Environments
• The collection of tools used in software development
• UNIX– An older operating system and tool
collection
• Borland JBuilder– An integrated development environment
for Java
• Microsoft Visual Studio.NET– A large, complex visual environment– Used to program in C#, Visual BASIC.NET,
Jscript, J#, or C++
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