Speed of light fibre optic signals which travel 30–40% slower at the speed of light through glass. There are different ways to determine the value of "c". One way is to measure the actual speed at which light waves propagate, which can be done in various astronomical and earth-based setups. However, it is also possible to determine "c" from other physical laws where it appears, for example, by determining the values of the electromagnetic constants "ε" and "μ" and using their relation to "c". Historically, the most accurate results have been obtained by separately determining the frequency and wavelength of a light beam,
Symbol table Symbol table In computer science, a symbol table is a data structure used by a language translator such as a compiler or interpreter, where each identifier (a.k.a. symbol) in a program's source code is associated with information relating to its declaration or appearance in the source. Symbol table stores the information related about the symbol. A symbol table may only exist in memory during the translation process, or it may be embedded in the output of the translation, such as in an ABI object file for later exploitation. For example, it might be used during an interactive debugging session, or