Page 190 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Unit 9: Software Development

Notes
Usually, an error in punching a card meant that the card had to be discarded
and a new one punched to replace it.
As time has progressed, computers have made giant leaps in the area of
processing power. This has brought about newer programming languages that
are more abstracted from the underlying hardware. Although these high-level
languages usually incur greater overhead, the increase in speed of modern
computers has made the use of these languages much more practical than in
the past. These increasingly abstracted languages typically are easier to learn
and allow the programmer to develop applications much more efficiently and
with less source code. However, high-level languages are still impractical for
a few programs, such as those where low-level hardware control is necessary
or where maximum processing speed is vital.

Throughout the second half of the twentieth century, programming was an
attractive career in most developed countries. Some forms of programming
have been increasingly subject to offshore outsourcing (importing software and
services from other countries, usually at a lower wage), making programming
career decisions in developed countries more complicated, while increasing
economic opportunities in less developed areas. It is unclear how far this
trend will continue and how deeply it will impact programmer wages and
opportunities.

9.1.1 Quality Requirements in Programming

Whatever the approach to software development may be, the final program must satisfy some
fundamental properties. The following properties are among the most relevant:
(a) Efficiency/performance: the amount of system resources a program consumes (processor
time, memory space, slow devices such as disks, network bandwidth and to some extent even
user interaction): the less, the better. This also includes correct disposal of some resources,
such as cleaning up temporary files and lack of memory leaks.
(b) Reliability: how often the results of a program are correct. This depends on conceptual
correctness of algorithms, and minimization of programming mistakes, such as mistakes
in resource management (e.g., buffer overflows and race conditions) and logic errors (such
as division by zero or off-by-one errors).
(c) Robustness: how well a program anticipates problems not due to programmer error. This
includes situations such as incorrect, inappropriate or corrupt data, unavailability of needed
resources such as memory, operating system services and network connections, and user
error.
(d) Usability: the ergonomics of a program: the ease with which a person can use the program
for its intended purpose or in some cases even unanticipated purposes. Such issues can
make or break its success even regardless of other issues. This involves a wide range of
textual, graphical and sometimes hardware elements that improve the clarity, intuitiveness,
cohesiveness and completeness of a program’s user interface.
(e) Portability: the range of computer hardware and operating system platforms on which the
source code of a program can be compiled/interpreted and run. This depends on differences
in the programming facilities provided by the different platforms, including hardware and
operating system resources, expected behaviour of the hardware and operating system, and
availability of platform specific compilers (and sometimes libraries) for the language of the
source code.

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