Machine language:-

The set of instruction codes, whether binary or in decimal notation, which can be directly understood by the computer without the help of translating program is called Machine code or Machine language program.
Computer can be programmed to understand much different computer language there is only one language understood by the computer without any translation program which: Machine code
Machine code is fundamental language of computer and is written in string of 0’s & 1’s.
An instruction prepared in any machine language has two parts:
(1) OPCODE (operation code)
(2) OPERAND (address location memory)
Advantage:
(1) Fastest execution:
A program written in machine language can be executed very fast by the computer as CPU graphs it easily.
Disadvantages:
(1) Machine dependent:
The internal design of every type of computer is different from every other     type of computer and needs different electrical signals to operate; machine language is different from computer to computer.
(2) Difficult to program:
It is necessary for the programmer either to memorize the dozens of codes for commands or to constantly refer to a reference card for preparing program the has to keep track of the storage location of data.
(3) Error prone:
As the programmer has to keep track of the storage location of data it becomes very difficult for him to concentrate fully on the logic of the problem. This results in error.
(4) Difficult to modify:
It is difficult to correct or modify machine language programs to correct it is a tedious job. Modifying a machine language program at a later date is so difficult that many programmers would prefer to code the new logic a fresh instead of incorporating the necessary modification.