Byte-code is a binary file containing an executable program, formed by a sequence of op code/data pairs.
Byte-code is a sort of intermediate code that is more abstract than machine code.
It is often treated as a binary file containing an executable program, much like an object module. Byte-code is called so because usually each opcode is one byte in length but the length of instruction code varies.
Each instruction has one byte operation code from 0 to 255 (or as hexadecimal: 00 to FF) followed by parameters such as registers or memory address.
This is a typical case, but the specification of bytecode largely varies in language.