[3.3.2 THE FUNCTION AND PURPOSE OF TRANSLATORS]
In earlier days, everything was programmed on the lowest level possible. In binary with 1 and 0 electrical signals that were physically turned on and off.
Not long after the first programming language was devised to make this job a bit easier, this was called assembly.
Assembly consisted of pre-set code words for binary byte combinations; they were in a look up table. These groups of values were known as mnemonics. They had a one to one relationship. One input gives out one output.
Very simple low-level languages can also be described as assembly languages.
The software involved in translating this low level language to the machine code is knows as the assembler and each computer chipset has its own unique assembler.