Questions/Review 1,2,3

Define lexeme and token.

Formal descriptions of the syntax of programming languages, for simplicity's sake, often do not include descriptions of the lowest-level syntactic

units. These small units are called lexemes.

So, a token

of a language is a category of its lexemes. For example, an identifier is a token

that can have lexemes, or instances, such as sum and total.

How are programming languages formally defined?

Two distinct ways: by recognition and by generation

In which form is the programming language syntax commonly described?

by context-free grammars.

What is a metalanguage?

A language that is used to describe another language

What is a derivation in the context of grammar?

the sequence of rule application

What is an ambiguous grammar?

A grammar that generates a sentential form for which there are two or more distinct parse trees

What is a left-recursive grammar?

When a grammar rule has its LHS also appearing at the beginning of its RHS, the rule is said to be left recursive

Explain the use of meta symbols in EBNFs.

Notational tools and not terminal symbols in the syntactic entities they help describe . These include brackets, braces, and parentheses in the EBNF extensions.

What is the purpose of a predicate function?

States the static semantic rules of the language and associated with grammar rules.

When can the parse tree be called fully attributed?

If all the attribute values in the parse tree have been computed

How is the order of evaluation of attributes determined for the trees of a given attribute grammar?

With the construction of a dependency graph to show all attribute dependencies.

What is the use of intrinsic attributes?

Can be used to compute the remaining attribute values.

What is meant by decorating a parse tree?

The process of computing the attribute values of a parse tree.

Why can machine languages not be used to define statements in operational semantics?

First the individual steps in the execution of machine language and the resulting changes to the state of the machine are too small and too numerous. Second the storage of a real computer is too large and complex. There are usually several levels of memory devices, as well as connections to enumerable other computers and memory devices through networks.

Describe the two levels of uses of operational semantics.

At highest level, the interest is in the final result of the execution of a complete program. This is sometimes called natural operational semantics.

At lowest level, operational semantics can be used to determine the precise meaning of a program through an examination of the complete sequence of state changes that occur when the program is executed. This is sometimes called structural operational semantics

In denotational semantics, what are the syntactic and semantic domains?

The domain is called the syntactic domain, because it is syntactic structures that are mapped. The range is called the semantic domain.

What is stored in the state of a program for denotational semantics?

The values of all of the program's variables.

What is an assertion in axiomatic semantics?

Describes the constraints on the program variables at that point in the program.

What two things must be defined for each language entity in order to

construct a denotational description of the language?

Both a mathematical object and a function that maps instances of that language entity onto instances of the mathematical object.

Which part of an inference rule is the antecedent?

The top part of an inference rule.

What is the weakest precondition?

The least restrictive precondition that will guarantee the validity of the associated postcondition.

What is an inference rule?

A method of inferring the truth of one assertion on the basis of the values of other assertions.

Give an example of a logical pretest loop.

Msl and Mb, that map statement lists and states to states and Boolean expressions to Boolean values (or error), respectively.

On what branch of mathematics is denotational semantics based?

Recursive function theory.

What is the problem with using a software pure interpreter for operational semantics?

The detailed characteristics of the particular computer would make actions difficult to understand. Such a semantic definition would be machine-dependent.

Explain what the preconditions and postconditions of a given statement mean in 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.

What is the difference between total correctness and partial correctness with regard to loop termination?

Because of the difficulty of proving loop termination, that requirement

is often ignored. If loop termination can be shown, the axiomatic description

of the loop is called total correctness. If the other conditions can be met but

termination is not guaranteed, it is called partial correctness.

When is a function called a predicate transformer?

When it takes a predicate, or assertion, as a parameter and returns another predicate.

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

Unlike operational semantics, denotational semantics does not model the step- by-step computational processing of programs.

What is the meaning of Plankalkül? Who developed Plankalkül?

Plankalkul means program calculus. German scientist Konrad Zuse developed it.

What was the simplest data type in Plankalkül?

The single bit

How did Plankalkül implement iterations?

It included a statement Fin, which used a superscript to specify a jump out of a given number of iteration loop nesting or to the beginning of a new cycle of iteration

Speedcoding was invented to overcome two significant shortcomings of the computer hardware of the early 1950s. What were they?

The computer hardware of that age never supported floating point operations and they did not allow some sort of indexing to use arrays easily.

Why was the technique used by Short Code called automatic programming?

It clearly simplified the programming process, but at the expense of execution time.

In what year was IBM 704 introduced?

1954

Where was Fortran developed? By whom?

Fortran was developed by John Backus at IBM

Under what environmental constraints was Fortran developed?

Computers had small memories and were slow and relatively unreliable, the primary use of computers was for scientific computations, there were no existing efficient and effective ways to program computers, and because of the high cost of computers compared to the cost of programmers, speed of the generated object code was the primary goal of the first Fortran compilers.

How were data types specified for variables in Fortran I?

Variables whose names began with I, J, K, L, M, and N were implicitly integer type, and all others were implicitly floating-point.

What was the most significant feature added to Fortran II to get Fortran IV?

explicit type declarations for variables

What syntactic changes did Fortran 90 include?

the required fixed format of code, which required the use of specific character positions for specific parts of statements, was dropped and only the first letter of keywords and identifiers would be uppercase

Which version of Fortran was the first to support object-oriented programming?

Fortran 2003

Which version of Fortran was the first to have local scopes?

Fortran 2008

Why was Fortran list processing language (FLPL) designed and implemented as an extension to Fortran?

FLPL was designed as an extension to Fortran to enhance its capabilities and address the specific needs of the scientific and engineering communities, allowing for more versatile and expressive programming while maintaining compatibility and interoperability with existing Fortran codebases.

Where was Lisp developed? By whom?

At MIT by John McCarthy

In what ways do Scheme and metalanguage (ML) differ from each other?

ML does not use the parenthesized functional syntax that originated with lambda expressions.

What are the features of F# that make it unique?

Some of the key features that make F# unique include:

Functional-First Paradigm, Type Inference, Interoperability, Immutable by Default, Pattern Matching, Concurrency and Parallelism, Units of Measure, Type Providers, Scripting and REPL, Cross-Platform, and is Open Source

What are the goals of the new language developed by GAMM and ACM?

It can smoothly interoperate with any other .NET language, it supports both functional programming and procedural programming, and it also fully supports object-oriented programming.

In what version of ALGOL did the concept of data type appear?

ALGOL 58

What were the most important modifications made to ALGOL 58?

The concept of block structure was introduced. Two different means of passing parameters to subprograms were allowed. Procedures were allowed to be recursive, and stack-dynamic arrays were permitted.

What change did ALGOL provide regarding input and output statements?

ALGOL introduced formatted input and output, allowing programmers to specify data formatting. This made code more readable and improved error handling, influencing later languages.

On what programming language was COBOL based?

FLOW-MATIC

In what year did the Basic design process begin?

1959

How does COBOL allow variable names to be truly connotative?

COBOL allows variable names to be truly connotative by supporting descriptive names. These names can reflect the meaning and purpose of variables in a way that makes the code self-explanatory.

What organization was most responsible for the early success of COBOL (in terms of extent of use)?

the Department of Defense (DoD)

What were the objectives behind developing Basic?

It must be easy for nonscience students to learn and use, It must be "pleasant and friendly.", It must provide fast turnaround for homework, It must allow free and private access, and It must consider user time more important than computer time.

Why is Alan Cooper known as "the father of Visual Basic"?

Cooper's program, combined with Microsoft's QuickBASIC language, became Visual Basic

What facilities did PL/I provide?

PL/I provided versatile facilities, combining features of different languages, including support for data types, I/O operations, and system-level programming.

What are the two fundamental characteristics shared by APL and SNOBOL?

dynamic typing and dynamic storage allocation

What features of SIMULA 67 are now important parts of some object-oriented languages?

the concept of a class and data abstraction

What innovation of data structuring was introduced in ALGOL 68 but is often credited to Pascal?

User defined data structures

What was the primary deficiency of ALGOL 60?

Orthogonality

Which language was used for teaching programming in the 1970s?

Pascal

What operators in C were modeled on similar operators in ALGOL 68?

The assignment operator,

Why is C both liked and disliked?

because of its lack of complete type checking.

What is a procedural language?

one that uses sets of functions and commands to complete actions.

What are the two kinds of statements that populate a Prolog database?

Facts and Rules

What is the primary application area for which Ada was designed?

The Department of Defense (DoD)

What are the concurrent program units of Ada called?

Tasks

What are the different mechanisms in C that show that it was influenced by ALGOL 68?

C was influenced by ALGOL 68, and some mechanisms that reflect this influence include structured control statements, block structure, and pass-by-value parameters.

Why did Ada 95 lose its popularity?

Ada 95 lost popularity due to complexity and the dominance of other languages like C and C++.

What is the meaning of operator overloading in C++?

allows operators to have different implementations for different data types, making code more intuitive and readable.

What additional feature did the release 3.0 of C++ provide?

templates: enabling generic programming by defining functions and classes that work with different data types.

From what language does Objective-C borrow its syntax for method calls?

Smalltalk

What is the primary application for Objective-C?

Mac OS X and iOS

What do the Ada and COBOL languages have in common?

Both are high level languages, both support object oriented programming, future versions of these languages support the program written in these language, both are not good for beginners, and both are frequently used for the applications but not user friendly.

What are threads in Java?

lightweight sub-processes that allow for concurrent execution in a Java program. They can run tasks independently and efficiently, enabling parallelism and multitasking.

What characteristic of Java is most evident in JavaScript?

Format of syntax

How does the typing system of PHP and JavaScript differ from that of Java?

Java is a strongly typed language while JavaScript and PHP are dynamically typed.

What array structure is included in C# but not in C, C++, or Java?

Jagged arrays

What are the characteristics of Perl's arrays?

ordered, flexible data structures that can store both numeric and string values. They have dynamic sizes and can hold mixed data types. Arrays are zero-indexed, and elements can be easily added or removed, making them versatile for various programming tasks.

For what application area is JavaScript most widely used?

Web applications

What is the relationship between JavaScript and PHP, in terms of their use?

JavaScript and PHP are both scripting languages used for web programming, Js used in the browser while PHP is used on the server.

PHP's primary data structure is a combination of what two data structures from other languages?

JavaScript's array and Perl's hashes

What data structure does Python use in place of arrays?

list

What characteristic does Ruby share with Smalltalk?

They are both purely object oriented

What characteristic of Ruby's arithmetic operators makes them unique among those of other languages?

Arithmetic operators can be re-defined

What is the similarity between Lua and JavaScript?

both lightweight, high-level scripting languages. They share similarities in terms of their minimalistic design, simplicity, and ease of integration into other applications. Additionally, both support dynamic typing and are often embedded as scripting engines in software and games.

Is Lua normally compiled, purely interpreted, or impurely interpreted?

Impurely interpreted

What deficiency of the switch statement of C is addressed with the changes made by C# to that statement?

At the end of selectable blocks of code, break statement was not mandatory

What is the primary platform on which C# is used?

.NET

What are the inputs to an XSLT processor?

An XML data document and an XSLT document

What is the output of an XSLT processor?

XML format document, HTML, or plain text

What element of the JSTL is related to a subprogram?

XML action element

To what is a JSP document converted by a JSP processor?

A servlet

Where are servlets executed?

In web server systems

Why is it useful for a programmer to have the ability to learn new

languages, even though he or she may have a good knowledge of a

number of programming languages?

Different languages might have different features that they specialize in. Learning more languages will help you understand the concepts better and be able to simulate them in other languages if you need to.

Why is it essential to choose an appropriate programming language for a

specific software solution?

Languages contain some features that are unique to them. These unique features makes it easier implement specific software solutions.

Which programming language for scientific applications was the first to

be used successfully?

Fortran

Which is the first successful high-level programming language for business?

Cobol

In which programming language were most of the AI applications

developed prior to 1990?

Lisp