Q & A
1. Why is it useful for a programmer to have some background in language
design, even though he or she may never actually design a programming language
Increased capacity to express ideas
Improved background for choosing appropriate languages.
Increased ability to learn new languages.
Better understanding of the significance of an implementation.
2. How can knowledge of programming language characteristics benefit the
whole computing community?
If those who choose a language,
are better informed, then perhaps better languages would eventually squeeze out
poorer ones.
3. What programming language has dominated scientific computing
over the past 45 years?
FORTRAN - FORTRAN has been used for
a long time for scientific computing. It was the first language for scientific
applications because FORTRAN provides efficiency which was the primary concern
for scientific applications.
4. What programming language has dominated business applications over the
past 45 years?
COBOL - COBOL was the first
successful high-level language for business. It is the most commonly used
language for business applications because business languages are
characterized by facilities for producing elaborate reports, precise ways of
describing, strong decimal numbers, character data and the ability to
specify decimal arithmetic operations.
5. What programming language has dominated artificial intelligence over
the past 45 years?
LISP - LISP which appeared in
1959.Artificial Intelligence (AI) is a broad area of computer applications
characterized by the used of symbolic rather than numeric computations.
6. In what language was UNIX written?
The UNIX operating system is written almost
entirely in C which has made it relatively easy to port, or move to different
machines. Some of the characteristics of C make it a good choice for systems
programming. It is low level, execution efficient and doesn’t burden the user
with many safety restrictions.
7.What is the disadvantage of having to many features in a language?
If a language has to many features, some programmers wont be familiar with them
all, leading to the misuse of some features and disuse of others.
8.How can user-defined operator overloading harm readability of a
program?
If a programmer doesn't do it sensibly, it can reduce readability.
9. What is one example of lack of orthogonality in the design of C?
Consider the following rules and exceptions in C. Although C has two kinds
of structured data-types arrays and records (structs). records can be any data
type except void or a structure of the same type. An array element can be any
data type except a void or a function. Parameters are passed by value, unless
they are arrays, in which they are , in effect, passed by reference.
10. What language used orthogonality as a primary design criterion?
ALGOL 68 - ALGOL 68 is the most
orthogonal programming language because every language constructs in ALGOL 68
has a type, and there are no restrictions on those types. But LISP can also be
said as a good combination of simplicity and orthogonality. LISP a functional
language is one in which computations are made primarily by applying a function
to a given program.
11. What primitive control statement is used to build more complicated
control statements in languages that lack them?
It is “goto”, but in the 1970s, the use of “goto”
statements was replaced by structured programming, which could be read from top
to bottom. (While, in newer languages)
12. What construct of a programming language provides process
abstractions?
Programming languages usually contain
abstractions for defining and manipulating data structures or
controlling the flow
of execution. The practical necessity that a programming language supports
adequate abstractions is expressed by the abstraction principal. This principle
is sometimes formulated as recommendation to the programmer to make proper use
of such abstractions.
13.What does it mean for a program to be reliable?
A program is said to be reliable if it performs to
its specifications under all conditions. Factors that affect reliability are
type checking, exception handling, aliasing, readability and write-ability
14. Why is
type checking the parameters of a subprogram important?
Type checking is important because run-time type
checking is expensive, compile-time type checking is more desirable.
Furthermore, the earlier errors in programs are detected, the less expensive it
is to make the required repairs..
15. What is
aliasing?
Aliasing is having two or more distinct names that
can be used to access the same memory cell. It is now widely accepted that
aliasing is a dangerous feature in a programming language. In some languages,
aliasing is used to overcome deficiencies in the language’s data abstraction
facilities.
16.What is
exception handling?
Exception handling is the ability of a program to
intercept run-time errors (as well as the unusual conditions detectable by the
program), take corrective measures, and then continue in an obvious aid to
reliability.
17. Why is
reliability important to write-ability?
Readability is important to write-ability because if
a programming language is difficult to read and understand then it can be
difficult for a programmer to create new code that might need to interact or
use other code. Often times code needs to be modified and if a program is
difficult to read then it is difficult to add new code to it.
18.How is the cost of compilers for a given language related to the design
of that language.
A language that requires many run-time type checks will prohibit fast code
execution, regardless of the quality of the compiler.
19. What has
been the strongest influence of programming language design over the past 50
years.
Most of the past 50 years have been designed
around the prevalent computer architecture, called the von Neumann
architecture, after one of its originators, John von Neumann.
20. What is
the name of the category of programming languages whose structure is dedicated
by the Von Neumann computer architecture?
These languages are called the imperative
languages.
21 What two
programming language deficiencies were discovered as a result of the research
in software development in the 1970s.
The late 1960s and early 70s brought intense analysis of software development. the result in
large begun the structure programming movement of both the software development
process and program language design.
An important reason for this research was the shift in the major cost of
computing from hardware to software. The primary
programming language deficiencies that were discovered were in-completeness of
type checking and inadequacy of control statements (requiring the extensive use
of gotos).
22. What are
the three fundamental features of Object-orientated programming language.
The three fundamentals features of an
object-oriented programming language are data abstraction, which encapsulates
processing with data objects and controls access to data, adds inheritance
and dynamic method binding. Inheritance is a powerful concept that greatly
enhances the potential reuse of existing software, thereby providing the
possibility of significant increases in software development productivity.
Dynamic (run-time) method binding allows more flexible use of inheritance.
23. What
language was the first to support the three fundamental features of the
object-orientated programming?
The first language that supported the three
fundamental features of object-oriented programming was Smalltalk. Although Smalltalk
never became as widely used as many other languages, support for
object-oriented programming is now part of most popular imperative languages,
including Ada 95, Java, C++ , and C#.
24. What is an
example of two language design criteria that are in direct conflict with each
other?
The example of two language design criteria that
are in direct conflict with each other are reliability and cost of execution.
For example the Java language definition demands that all references to array
elements be checked to ensure that the index or indices are in their legal
ranges. This step adds a great deal to the cost of execution of Java programs
that contain large numbers of references to array elements. C does not require
index range checking, so C programs execute faster than semantically equivalent
Java programs, although Java programs are more reliable. The designers of Java
traded execution efficiency for reliability.
25. What are
the three general methods of implementing a programming language?
The three general methods of implementing a
programming language are compilation (programs are translated into machine
language), pure interpretation (programs are translated by another programs
known as interpreter), and Hybrid Implementation (a compromise between compilers
and pure interpreter).
26. Which
produces faster program execution, a compiler or pure interpreter?
A compiler, as a compiler translates directly into machine code.
27. What role
does a symbol table play in a compiler?
The symbol table serves as a database for the
compilation process. The primary contents of the symbol table are the type and
attribute information of each user-defined name in the program. This
information is placed in the symbol table by the lexical and syntax analyzers
and is used by the semantic analyzer and the code generator.
28. What does
a linker do?
Most user programs also require programs from the operating system. Among
the most common of these are programs for input and output. The compiler builds
calls to required system programs when they are needed by the user program.
Before the machine language programs produced by a compiler can be executed. The required programs from the operating system must be found and linked to the
user program. The process of collecting system programs and linking them to
user programs is called linking and loading or just linking. in addition user
programs may have to be linked to other user programs.
29.Why is the
Von Neumann bottleneck important?
The speed of the connection between a computers memory and its processor
usually determines the the speed of the computer, because instructions often
can be executed faster than they can be moved to the processor for
execution. This connection is called the von Neumann bottleneck; it is the
primary limiting factor in the speed of von Neuman architecture computers, The
von Neumann bottleneck has been one of the primary motivations for the research
and development of parallel computers.
30. What are
the advantages of implementing a language with pure interpreter?
The advantages of a pure interpreter, is allowing easy implementation of many source level debugging
operations, because all run time errors messages can refer to source level
units.
