Pair programming

Pair programming is an agile software development technique in which two programmers work together at one workstation. One, the driver, writes code while the other, the observer or navigator,reviews each line of code as it is typed in. The two programmers switch roles frequently.

While reviewing, the observer also considers the "strategic" direction of the work, coming up with ideas for improvements and likely future problems to address. This frees the driver to focus all of his or her attention on the "tactical" aspects of completing the current task, using the observer as a safety net and guide.

Pair programming increases the man-hours required to deliver code compared to programmers working individually. Experiments yielded diverse results, suggesting increases of between 15% and 100%. However, the resulting code has about 15% fewer defects. Along with code development time, other factors like field support costs and quality assurance also affect the expenses. IBM reported spending about “$250 million repairing and reinstalling fixes to 30,000 customer-reported problems”. Pair programming significantly reduces these expenses by reducing the defects in the programs.

A system with two programmers possesses greater potential for the generation of more diverse solutions to problems for three reasons:

In an attempt to share goals and plans, the programmers must overtly negotiate a shared course of action when a conflict arises between them. In doing so, they consider a larger number of ways of solving the problem than a single programmer alone might do. This significantly improves the design quality of the program as it reduces the chances of selecting a poor method.

In an online survey of pair programmers, 96% of them stated that they enjoyed their work more than when they programmed alone and 95% said that they were more confident in their solutions when they pair programmed.

Knowledge is constantly shared between pair programmers, whether in the industry or in a classroom, many sources suggest that students show higher confidence when programming in pairs, and many learn whether it be from tips on programming language rules to overall design skill. In "promiscuous pairing", each programmer communicates and works with all the other programmers on the team rather than pairing only with one partner, which causes knowledge of the system to spread throughout the whole team. Pair programming allows the programmers to examine their partner's code and provide feedback which is necessary to increase their own ability to develop monitoring mechanisms for their own learning activities.

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Wikipedia