Machine code, also known as machine language, is a low-level programming language consisting of binary or hexadecimal instructions that execute computer programs on the CPU. It is the lowest level of code and communicates the programs instructions in the form of software directly to the hardware of the computer via the CPU. Each instruction in machine code causes the CPU to perform a specific task, such as a load, a store, a jump, or an arithmetic logic unit (ALU) operation on one or more units of data in the CPUs registers or memory.

Machine code is the binary representation of a computer program that is read and interpreted by the computer. Every computer processor has its own instruction set designed to process machine code, and each CPU has its specific machine language. The architecture of the particular processor determines how instructions are patterned, and the execution of instructions is controlled by firmware or the CPUs internal wiring.

In the early days of programming, applications were written directly in machine code, but as that method of developing applications is tedious and inefficient, programmers developed new higher-level programming languages like C, Java, and Python to be processed by compilers and turned into machine code for execution in the CPU. Nowadays, human programmers rarely, if ever, deal directly with machine code anymore.