Code Review: What-Why-Who-When-How

What

Code Review is an activity in which people other than the author of a code examine it for:

Identify Defects
Discover for Improvement opportunities

Objective of code review in a team leads creating and maintaining a consistent, structured, and standardized codebase. Nothing more, nothing less

Why

The benefits or the goals of code review are the following:

Finding bugs as early as possible, so they are economical to fix.
Coding standards conformity, Code review helps to maintain consistent coding style across the project/company.
Knowledge sharing, during review team members, gain a better understanding of the source code.
Consistent design, review helps to maintain a level of consistency in software design.
Software security, applications that require a high level of security can be targeted for security reviews.
Team Building. Review discussions save team members from isolation and help them to know each other and bring them closer.

Who

Role	Responsibility
Author	Write code for code review Takes Responsibility for initiating/following up for code review Inform reviewer that product is ready for review Apply changes recommended by the reviewer Track the invested time for review and changes
Project Manager	Planning and managing code review process Identify reviewer Schedule code review activity Ensure review occurred as planned Arrange/provide training if required
Reviewer	Prepare a review checklist Perform code review Document all identified issue Share findings with Author

When

Pre-commit/Check-In review is a form of code review where code is reviewed before going into the codebase. Code is shared with the Reviewer and the reviewer reviews it and shares their comments directly with the developer. Once all comments are implemented the code is committed to the repository.
Post-commit/Check-In review is where the code is reviewed after going into the codebase. The code is committed to the repository and the reviewer takes the code into the repository and shares his/her comment on this with the developer. Fixes are made and again committed in the codebase.

The advantage of pre-commit review over post-commit review is that mistakes are caught early and pose less cost. As a consequence development takes more time.

How

Manual

Based on the pre-prepared review checklist
Code Walkthrough
Conducted manually
Risk of human error

Automated

Fast as compare to manual with a predefined set of rules or best practices.
Based on reports generated by the tool action items are identified.
Popular tools FXCop and NDepend

Techniques Comparison

Criteria	Manual	Automated
Review Time	Comparatively High	Comparatively Low
Initial Setup Time	Minimal	Require setup time for initial configuration
Technology Dependence	Independent	Dependent
Price Involved	Only human resource cost	Incorporates tool cost

Focus Areas

Review fewer than 200–400 lines of code at a time
Aim for an inspection rate of fewer than 300–500 LOC per hour
Never review code for more than 90 minutes at a stretch
Establish quantifiable goals for code review, and capture metrics so you can improve your processes
Use checklists, because they substantially improve results for both authors and reviewers
Verify that the defects are actually fixed
Establish quantifiable goals for code review and capture metrics so you can improve your processes

Conclusion

I'd like to end my thoughts on the code review process with the following:

For the reviewer: Focus on the code, not the developer!
For the developer: Don’t take it as a critic of your coding skills, but as an exercise to improve the code in the codebase.