A coding interview, technical interview, programming interview or Microsoft interview is a technical problem-based
job interview
A job interview is an interview consisting of a conversation between a job applicant and a representative of an employer which is conducted to assess whether the applicant should be hired. Interviews are one of the most popularly used devices for ...
technique to assess applicants for a
computer programming
Computer programming is the process of performing a particular computation (or more generally, accomplishing a specific computing result), usually by designing and building an executable computer program. Programming involves tasks such as anal ...
or
software development
Software development is the process of conceiving, specifying, designing, programming, documenting, testing, and bug fixing involved in creating and maintaining applications, frameworks, or other software components. Software development inv ...
position. Modern coding interview techniques were pioneered by
Microsoft
Microsoft Corporation is an American multinational corporation, multinational technology company, technology corporation producing Software, computer software, consumer electronics, personal computers, and related services headquartered at th ...
during the 1990s
and adopted by other large technology companies including
Amazon
Amazon most often refers to:
* Amazons, a tribe of female warriors in Greek mythology
* Amazon rainforest, a rainforest covering most of the Amazon basin
* Amazon River, in South America
* Amazon (company), an American multinational technolog ...
,
Facebook
Facebook is an online social media and social networking service owned by American company Meta Platforms. Founded in 2004 by Mark Zuckerberg with fellow Harvard College students and roommates Eduardo Saverin, Andrew McCollum, Dustin ...
, and
Google
Google LLC () is an American Multinational corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...
. Coding interviews test candidates' technical knowledge, coding ability, problem solving skills, and creativity, typically on a
whiteboard
A whiteboard (also known by the terms marker board, dry-erase board, dry-wipe board, and pen-board) is a glossy, usually white surface for making non-permanent markings. Whiteboards are analogous to blackboards, but with a smoother surface all ...
. Candidates usually have a degree in
computer science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (includin ...
,
information science
Information science (also known as information studies) is an academic field which is primarily concerned with analysis, collection, classification, manipulation, storage, retrieval, movement, dissemination, and protection of information. ...
,
computer engineering
Computer engineering (CoE or CpE) is a branch of electrical engineering and computer science that integrates several fields of computer science and electronic engineering required to develop computer hardware and software. Computer enginee ...
or
electrical engineering, and are asked to solve
programming problems,
algorithms
In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...
, or
puzzle
A puzzle is a game, problem, or toy that tests a person's ingenuity or knowledge. In a puzzle, the solver is expected to put pieces together ( or take them apart) in a logical way, in order to arrive at the correct or fun solution of the puzzle ...
s.
Coding interviews are typically conducted in-person or virtually.
Innovation
Microsoft's interview style was distinctive in that it concerned technical knowledge, problem solving and creativity as opposed to the
goal and weaknesses interviews most companies used at the time. Initially based on
Bill Gates
William Henry Gates III (born October 28, 1955) is an American business magnate and philanthropist. He is a co-founder of Microsoft, along with his late childhood friend Paul Allen. During his career at Microsoft, Gates held the positions ...
's obsession with puzzles, many of the puzzles presented during interviews started off being
Fermi problem
In physics or engineering education, a Fermi problem, Fermi quiz, Fermi question, Fermi estimate, order-of-magnitude problem, order-of-magnitude estimate, or order estimation is an estimation problem designed to teach dimensional analysis or ...
s, or sometimes logic problems, and have eventually transitioned over the years into questions relevant to programming.
As
William Poundstone
William Poundstone is an American author, columnist, and skeptic. He has written a number of books including the '' Big Secrets'' series and a biography of Carl Sagan
Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American a ...
wrote, "Puzzles test competitive edge as well as intelligence. Like business or football, a logic puzzle divides the world into winners and losers. You either get the answer, or you don't. … Winning has to matter."
Questions
The questions asked during a coding interview are crafted to determine a candidate's problem solving, coding and design abilities. Eccentric questions (such as "Which of the fifty states would you remove?") test a candidate's ability to come to a decision and articulate it.
Candidates answering questions should consider the use of technology in the present and future, and
user scenarios
In computing, a scenario (, ; loaned (), ) is a narrative of foreseeable interactions of user roles (known in the Unified Modeling Language as ' actors') and the technical system, which usually includes computer hardware and software.
A scena ...
. Some questions involve projects that the candidate has worked on in the past.
A coding interview is intended to seek out creative thinkers and those who can adapt their solutions to rapidly changing and dynamic scenarios.
Typical questions that a candidate might be asked to answer during the second-round interview include:
* Design a GPS navigation unit for a hiker.
* Design a communication device for Canadian park rangers.
* Shift all elements of a circular array by ''k'' bytes, using no extra memory.

Microsoft popularized the question of why
manhole covers
A manhole cover or maintenance hole cover is a removable plate forming the lid over the opening of a manhole, an opening large enough for a person to pass through that is used as an access point for an underground vault or pipe. It is designed t ...
are typically round (in some countries) when they began asking it as a job interview question.
Originally meant as a psychological assessment of how one approaches a question with more than one correct answer, the problem has produced a number of alternative explanations, from the
tautological ("Manhole covers are round because manholes are round.")
to the philosophical.
By 2012, the practice of asking
lateral thinking
Lateral thinking is a manner of solving problems using an indirect and creative approach via reasoning that is not immediately obvious. It involves ideas that may not be obtainable using only traditional step-by-step logic. The term was first u ...
questions had declined at companies including Microsoft and Google. A study by
San Francisco State University
San Francisco State University (commonly referred to as San Francisco State, SF State and SFSU) is a public research university in San Francisco. As part of the 23-campus California State University system, the university offers 118 different b ...
associate professor of psychology Chris Wright found that puzzle interview questions annoyed job applicants. "Methods that had a transparent relationship between test content and job duties, such as interviews, work samples, and reference checks were perceived more favorably," Wright wrote in a research paper entitled "Why Are Manhole Covers Round? A Laboratory Study of Reactions to Puzzle Interviews". Poundstone, who had written puzzle interview guides for Microsoft and Google, referred to puzzle questions in 2012 as "a sort of fad" that lost popularity because of a lack of evidence of their effectiveness.
References
Microsoft culture
Job interview
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