Mainframes
Mainframes are the correct answer for the question "Which of the following is used in EBCDIC?" EBCDIC (Extended Binary Coded Decimal Interchange Code) is a character encoding system that is used primarily on IBM mainframe computers.

Character Encoding System
A character encoding system is a method that is used to represent characters in a digital format. It assigns unique numeric codes to each character, allowing them to be stored and processed by computers. Different character encoding systems have been developed over the years, with some being specific to certain computer architectures or manufacturers.

EBCDIC
EBCDIC is one such character encoding system that was developed by IBM in the 1960s. It was designed to be used on their mainframe computers, which were widely used in large organizations and government agencies at the time. EBCDIC uses 8 bits to represent each character, allowing for a total of 256 possible characters.

Usage and Compatibility
EBCDIC was widely used in the past, particularly in mainframe environments. It was the default character encoding system for IBM mainframes and was used for a variety of purposes, including data storage, communication protocols, and input/output operations. However, with the rise of more modern computing platforms and standards, the usage of EBCDIC has declined over the years.

ASCII vs EBCDIC
ASCII (American Standard Code for Information Interchange) is another popular character encoding system that is widely used today. It is used in most personal computers and many other computing devices. ASCII and EBCDIC are not compatible with each other, meaning that a character represented in ASCII may have a different code in EBCDIC.

Conclusion
In conclusion, the correct answer to the question "Which of the following is used in EBCDIC?" is Mainframes. EBCDIC is a character encoding system that was primarily used on IBM mainframe computers and is not compatible with ASCII.