Code that is written (then assembled as zeros and ones), line by line, using English-like mnemonics such as IN, OUT, LDA, STA, ADD, CMP, JMP, NOP etc, with each mnemonic corresponding to a number found in the internal, numeric list of a machine code instruction set. Each instruction uses a certain number of machine cycles to complete its task, regulated by the computer's timing device or "clock".
Click here for a list of mnemonics (and what they meant) as used in the original 8-bit Intel 8080 processing chip.
Click here for the full numeric list, including the number of machine cycles for each operation.
Click here for further information on Assembly Language.