std::cout vs std::cerr

Understanding output streams in C++

This is an easy foundational question about C++ standard library streams. It tests whether you understand the purpose and behaviour of the two most common output channels in a C++ program, and why a professional codebase distinguishes between them.

The question probes practical knowledge that matters in both interview settings and production code. In trading systems and data-processing pipelines, correct use of output streams affects logging, debugging, and system monitoring. Interviewers ask this to confirm you grasp the standard library's design philosophy around separate channels for normal output versus error reporting.

• Stream buffering and synchronisation
• Stream redirection in Unix/shell environments
• Logging and diagnostics best practices