Programming Domains
1. Scientific Applications
Typically, scientific applications have
simple data structures but require large
numbers of floating-point arithmetic
computations.
For some scientific applications where
efficiency is the primary concern, like
those that were common in the 1950’s
and 1960’s, no subsequent language is
significantly better than FORTRAN.
.

Programming Domains (con’d)
Business Applications
The use of computers for business applications
began in the 1950’s.
The first successful high-level language for
business was COBOL which appeared in 1960.
Business languages are characterized, according
to the needs of the application, by elaborate
input and output facilities and decimal data
types.
With the advent of microcomputers came new
ways of businesses, especially small
businesses, to use computers. Two specific
tools, spreadsheet systems and database
systems, were developed for business and now
are widely used.

Programming Domains (con’d)
Artificial Intelligence
AI is a broad area of computer applications characterized by
the absence of exact algorithms and the use of symbolic
computations rather than numeric computation.
Symbolic computation means that symbols, consisting of
names rather than numbers, are manipulated.
The first widely used programming language developed for AI
applications was the functional language LISP (Scheme)
which appeared in 1959.
An alternative approach to these applications appeared in the
early 1970’s: logic programming using Prolog language

Programming Domains (con’d)
Systems Programming Languages
The operating system and all of the programming
support tools of a computer system are collectively
known as its systems software.
Systems software is used almost continuously and
therefore must have execution efficiency.
A language for this domain must have low-level features
that allow the software to external devices to be
written.
In the 1960’s and 1970’s, some computer
manufacturers, such as IBM, Digital, and Burroughs
(now UNISYS) developed special machine-oriented
high level languages for systems software on their
machines. For IBM mainframe computers, the
language was PL/S, a dialect of PL/I; for Digital, it Is
BLISS, a language at a level just above assembly
language; for Burroughs, it was Extended Algol.
The UNIX operating system is written almost entirely in
C, which was made it relatively easy to port, or move,
to different machines.

Programming Domains (con’d)
Very High-level Languages (VHLLs)
The languages in the category called very high-level
have evolved slowly over the past 25 years.
The various scripting languages for UNIX are
examples of VHLLs. A scripting language is one
that is used by putting a list of commands, called
script, in a file to be executed.
The first of these languages, named shell, began as
a small collection of commands that were
interpreted to be calls to system subprograms that
performed utility functions, such as file
management and simple file filtering.
Other VHLLs are awk, for report generation, tcl
combined with tk, which provide a method of
building X Windows applications. The perl is a
combination of shell and awk.

Programming Domains (con’d)
• Special-Purpose Languages
– A host of special-purpose languages have appeared over
the past 40 years.
– They range from RPG, which is used to produce
business reports, to APT, which is used for instructing
programmable machine tools, to GPSS, which is used for
systems simulation.

Language Evaluation Criteria
• Readability
• Writability
• Reliability
• Cost

Readability
• The ease with which programs can be read and understood.
• Overall Simplicity – A language that has a large number of basic
components is more difficult to learn than one with a small number of basic
componenets.
examples: C
count = count + 1
count += 1
count++
++count
• Orthogonality – in a programming language means that a relatively small
set of primitive constructs can be combines in a relatively small number of
ways to build the control and data structures of the language
– Orthogonality is closely related to simplicity. The more orthogonal the design of a
language, the fewer exceptions the language rules require. Fewer exceptions
means a higher degree of regularity in the design, which makes the language
easier to learn.

Readability
• Control Structures. The structured
programming revolution of the 1970s was
a reaction to the poor readability caused
by the limited control statements of some
of the languages of the 1950s and 1960s.
– Examples
• Goto statements vs Loops

Readability
• Data Types and Structures.
– The presence of adequate facilities for
defining data types and data structures in a
language is another significant aid to
readability.

Readability
• Syntax Considerations
– The syntax, or form, of the elements of a
language has a significant effect on the
readability of programs.
– Examples:
• Identifier Forms (length, case sensitivity)
• Special Words (* & + %)
• Form and Meaning (Appearance does not always
suggest their function?)

Writability
Writability is a measure of how easily
a language can be used to create
programs for a chosen problem
domain.

Writability
• Simplicity and Orthogonality
• Support for Abstraction
– Abstraction means the ability to define and
then use complicated structures or operations
in ways that allow many of the details to be
ignored.
– Process abstraction
– Data abstraction

Writability
• Expressivity
– Expressivity in a language means that there
are very powerful operators that allow a great
dean of computation to be accomplished with
a very small program.

Reliability
• Type checking
– Type checking is simply testing for type errors
in a given program, either by the compiler or
during program execution
• Exception Handling
• Aliasing
• Readability and Writability

Cost
• The ultimate total cost of a programming
language is a function of many of its
characteristics.
– Cost of training programmers
– Cost of writing programs in the language
– Cost of compiling programs
– Cost of executing programs
– Cost of compilers
– Cost of poor reliability