What is C standard? 
The latest C standard is ISO/IEC 9899:2011, also known as C11 as the final draft was published in 2011. Before C11, there was C99. 

C is a general-purpose programming language that was developed in the early 1970s by Dennis Ritchie at Bell Labs. It is a low-level language that allows for direct manipulation of computer hardware and is widely used in system programming and for writing operating systems.

The C programming language is governed by a set of standards, which define its syntax, semantics, and behavior. These standards are maintained by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC), and are collectively referred to as the C programming language standard.

The current version of the C programming language standard is C18, which was approved in 2018. The C18 standard includes new features and updates to the previous standard, C11, including new library functions, improved support for Unicode, and better alignment with modern hardware architectures.

Programs written in compliance with the C standard are guaranteed to be portable and interoperable across different platforms and architectures. This means that a C program written for one system can be compiled and run on another system without modification, as long as both systems conform to the C standard.

In summary, the C programming language standard is a set of guidelines and rules that define the syntax, semantics, and behavior of the C language. Adhering to these standards ensures that C programs are portable and interoperable, and helps to promote consistency and reliability in software development.