“In computer design three levels can be distinguished: architecture, implementation and realisation; for the ﬁrst of them, the following working deﬁnition is given: The architecture of a system can be defined as the functional appearance of the system to the user, its phenomenology.”

— Gerrit Blaauw

Although the term architecture was introduced only ten years ago in computer technology (Buchholz), the concept of architecture is as old as the use of mechanism by man. When a child is taught to look at a clock, it is taught the architecture of the clock. It is told to observe the position of the short and the long hand and to relate these to the hours and the minutes. Once it can distinguish the architecture from the visual appearance, it can tell time as easily from a wrist watch as from the clock on the church tower.
The inner structure of a system is not considered by the architecture: we do not need to know what makes the clock tick, to know what time it is. This inner structure, considered from a logical point of view, will be called the implementation, and its physical embodiment the realisation.
Source: Computer architecture (1972), p. 154

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Gerrit Blaauw5

Dutch computer scientist 1924–2018

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“The architecture of a system can be defined as the functional appearance of the system to the user.”

Gerrit Blaauw (1924–2018) Dutch computer scientist

Blaauw (1972) cited in: Gerritt A Blaauw (1976) Digital system implementation. p. 6

“The design of a digital system starts with the specification of the architecture of the system and continues with its implementation and its subsequent realisation… the purpose of architecture is to provide a function. Once that function is established, the purpose of implementation is to give a proper cost-performance and the purpose of realisation is to build and maintain the appropriate logical organisation.”

Gerrit Blaauw (1924–2018) Dutch computer scientist

Source: Specification of Digital Systems (1978), p. 29

“The software architecture of a system or a family of systems has one of the most significant impacts on the quality of an organization's enterprise architecture. While the design of software systems concentrates on satisfying the functional requirements for a system, the design of the software architecture for systems concentrates on the nonfunctional or quality requirements for systems. These quality requirements are concerns at the enterprise level. The better an organization specifies and characterizes the software architecture for its systems, the better it can characterize and manage its enterprise architecture. By explicitly defining the systems software architectures, an organization will be better able to reflect the priorities and trade-offs that are important to the organization in the software that it builds.”

Scott W. Ambler (1966) Canadian software engineer/consultant/author

James McGovern, Scott W. Ambler and M. E Stevens (2004) A Practical Guide to Enterprise Architecture. p. 35

“Form - as a pattern of perception - can motivate the use of architecture. Architecture provides a complete service for its users, if function (practical purpose) coincides with use motivated by form.”

Justus Dahinden (1925) Swiss architect

Man and Space - Mensch und Raum 2005

“The term architecture is used here to describe the attributes of a system as seen by the programmer, i. e., the conceptual structure and functional behavior, as distinct from the organization of the data flow and controls, the logical design, and the physical implementation. i. Additional details concerning the architecture”

Gene Amdahl (1922–2015) American physicist

Gene Amdahl, Gerrit Blaauw, and Fred Brooks (1964) " Architecture of the IBM System http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.72.7974&rep=rep1&type=pdf." in: IBM Journal of Research and Development Vol 8 (2) p. 87-101

Fred Brooks (1931) American computer scientist

Gene Amdahl, Gerrit Blaauw, and Fred Brooks (1964) "Architecture of the IBM System." in: IBM Journal of Research and Development Vol 8 (2) p. 87-101.

“With increasing size and complexity of the implementations of information systems, it is necessary to use some logical construct (or architecture) for defining and controlling the interfaces and the integration of all of the components of the system.”

John Zachman (1934) American computer scientist

Source: A Framework for Information Systems Architecture, 1987, p. 276, cited in: CM Pereira (2004), "A method to define an Enterprise Architecture using the Zachman Framework". in: SAC '04 Proceedings of the 2004 ACM symposium on Applied computing. pp. 1366-1371

“There always is an architecture, whether it is defined in advance - as with modern computers - or found out after the fact - as with many older computers. For architecture is determined by behavior, not by words. Therefore, the term architecture, which rightly implies the notion of the arch, or prime structure, should not be understood as the vague overall idea. Rather, the product of the computer architecture, the principle of operations manual, should contain all detail which the user can know, and sooner or later is bound to know.”

Gerrit Blaauw (1924–2018) Dutch computer scientist

Source: Computer architecture (1972), p. 155

“Architecture is defined as the art and science of creating buildings. Systems engineering may be similarly defined as the art and science of creating systems.”

Derek Hitchins (1935) British systems engineer

Source: Advanced Systems Thinking, Engineering and Management (2003), p. 309; partly cited in: Kurt A. Richardson, Wendy J. Gregory, Gerald Midgley (2006) Systems Thinking and Complexity Science. p. 39

“Although many popular information systems planning methodologies, design approaches, and various tools and techniques do not preclude or are not inconsistent with enterprise-level analysis, few of them explicitly address or attempt to define enterprise architectures. Some examples of such popular offerings include”

John Zachman (1934) American computer scientist

Planning Methodologies: Stage Assessment, Critical Success Factors, Strategy Set Transformation, etc.
Design Approaches: Structured Analysis, Entity-Relationship Approaches, etc.
Tools and Techniques"Problem Statement Language/Problem Statement Analyzer (PSL/PSA), Prototype Development Methodology, Structured Analyses and Design Techniques, etc.
From an historical perspective, BSP and BICS likely will be looked back on as primitive attempts to take an explicit, enterprise-level architectural approach to information systems.
Source: Business Systems Planning and Business Information Control Study: A comparison, 1982, p. 32

“In computer design three levels can be distinguished: architecture, implementation and realisation; for the ﬁrst of them, the following working deﬁnition is given: The architecture of a system can be defined as the functional appearance of the system to the user, its phenomenology.”

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