Lecture 1 - part 2 - CIS430

ISBN 0-321-49362-1

Chapter 1

Preliminaries

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1-2

Chapter 1 Topics

•

Reasons for Studying Concepts of
Programming Languages

•

Programming Domains

•

Language Evaluation Criteria

•

Influences on Language Design

•

Language Categories

•

Language Design Trade-Offs

•

Implementation Methods

•

Programming Environments

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Language Categories

•Imperative
– Central features are variables, assignment statements, and

iteration

– Include languages that support object-oriented programming
– Include scripting languages
– Include the visual languages
– Examples: Python, C, Java, Perl, JavaScript, Visual BASIC .NET,

C++

•Functional
– Main means of making computations is by applying functions to

given parameters

– Examples: LISP, Scheme, ML, F#

•Logic
– Rule-based (rules are specified in no particular order)
– Example: Prolog

•Markup
– A set of rules that defines how the layout and presentation of

text and images should appear in a digital document.

– Examples: XML, HTML, LaTeX, MathML, JSON

Multiple Choice

XML stands for?

• Hypertext Markup Language

• Extensible Machine Language

• Extensible Markup Language

• None of these

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Language Design Trade-Offs

• Reliability vs. cost of execution

– Example: Java demands all references to array elements

be checked for proper indexing, which leads to increased
execution costs

• Readability vs. writability

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

n ← 4 5 6 7

n+4

8 9 10 11

• Writability (flexibility) vs. reliability

– Example: C++ pointers are powerful and very flexible but

are unreliable

Multiple Choice

LISP belongs to which programming language category?

• Imperative

• Functional

• Markup

• Logic

APL - Readability vs. writability

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APL - Readability vs. writability

VAR

sum,ARRAY data[1..500] OF REAL

i INTEGER;

BEGIN

WRITE('Number of data=..');

READLN(n);

sum:=0;

FOR i:=1 TO n DO

BEGIN

READ(data[i]);

sum:=sum+data[i]

END;

WRITELN(sum);

END.

but in APL you simply program the sum of inputs (no need for loops) as: ,

and the mean is also very tersely formulated as:

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(+/X)÷⍴X

Multiple Choice

It is easier to be an expert in APL compared to Pascal?

• True

• False

Multiple Choice

If x is an array in APL, then ⍴X means?

• Sum of the elements in array x

• Number of the elements in array x

• Average of the elements in array x

• Product of the elements in array x