This lecture covers the fundamental concepts of standard input and output in the C programming language. It begins by explaining how a program interacts with the external environment through input/output instructions and data streams. The instructor introduces the standard input (stdin) and output (stdout) streams defined in stdio.h, emphasizing their roles in reading from the keyboard and writing to the screen. The lecture details the printf function, including its format specifiers and return values, and provides examples of formatted output. The discussion extends to the scanf function, highlighting its similarities to printf while noting key differences, such as handling whitespace and reading specific character sets. The instructor also addresses the importance of error handling and controlling input to avoid infinite loops. Finally, the lecture introduces file handling in C, explaining how to associate file streams with physical files using fopen, and discusses the significance of the standard error stream (stderr) for error messages. Overall, this lecture provides a comprehensive overview of managing input and output in C programming.