Page 154 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Introduction to Microprocessors

Notes
CPI 8-bit Compare immediate with Accumulator
(a) It.is 2-byte instruction
(b) Second type is 8-bit data
(c) Compares second byte with (A)
(d) If (A) < 8-bit data, CY flag is set and zero flag
is reset
(e) If (A) = 8-bit data, zero flag is set and CY flag
is reset
(f) If (A) > 8-bit data, CY and zero flags are reset
(g) No contents are modified
(h) All remaining flags i.e., S, P, AC are affected
according to the result of subtraction.

Human-Computer Interaction (HCI)

uman-computer interaction (HCI) is an area of research and practice that emerged
in the early 1980s, initially as a specialty area in computer science. HCI has expanded
Hrapidly and steadily for three decades, attracting professionals from many other
disciplines and incorporating diverse concepts and approaches. To a considerable extent,
HCI now aggregates a collection of semi-distinct fields of research and practice in human-
centered informatics. However, the continuing synthesis of disparate conceptions and
approaches to science and practice in HCI has produced a dramatic example of how different
epistemologies and paradigms can be reconciled and integrated.

Until the late 1970s, the only humans who interacted with computers were information
technology professionals and dedicated hobbyists. This changed disruptively with the
emergence of personal computing around 1980. Personal computing, including both personal
software (productivity applications, such as text editors and spreadsheets, and interactive
computer games) and personal computer platforms (operating systems, programming
languages, and hardware), made everyone in the developed world a potential computer user,
and vividly highlighted the deficiencies of computers with respect to usability for those who
wanted to use computers as tools.
The challenge of personal computing became manifest at an opportune time. The broad project
of cognitive science, which incorporated cognitive psychology, artificial intelligence, linguistics,
cognitive anthropology, and the philosophy of mind, had formed at the end of the 1970s. Part
of the programme of cognitive science was to articulate systematic and scientifically-informed
applications to be known as “cognitive engineering”. Thus, at just the point when personal
computing presented the practical need for HCI, cognitive science presented people, concepts,
skills, and a vision for addressing such needs. HCI was one of the first examples of cognitive
engineering.
Other historically fortuitous developments contributed to establishment of HCI. Software
engineering, mired in unmanageable software complexity in the 1970s, was starting to focus
on nonfunctional requirements, including usability and maintainability, and on non-linear
software development processes that relied heavily on testing. Computer graphics and
information retrieval had emerged in the 1970s, and rapidly came to recognize that interactive
systems were the key to progressing beyond early achievements. All these threads of

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