A .xlsx file tells you that the file is an Excel workbook that utilizes XML files to create the various spreadsheets as well as macros and other hidden codes used to perform certain functions (which is why there's an X at the end; older .xls files had no indication of this external code being present, which is why they're almost never recommended for modern use).
Answer: Protocol
Explanation: Protocol is the standard that is used in the communication and electronic devices for the communication. Through the mean of the these guidelines the communication is done by the sending and receiving of the data.
This works for the both wired networking and wireless communication which functions under the certain conditions.Examples-TCP(Transmission control protocol), FTP(File transfer protocol) etc.
Characteristics
based on vaccum tubes
they were large,slow,low capacity
Magnetic drums for primary memory
used mll
input punched cards and output printsout
expensive
get heated faster
eg. ENIAC,UNIVAC
Answer: you can't
Explanation: The best way to make one is to search for one then copy and paste
Hope this helps^^