An assembler program, also known as an assembly language program, is a low-level programming language used to write software for computers. Synonyms for an assembler program include assembly code, machine language code, and assembly program. Assembly code refers to the human-readable instructions that are converted into machine code by the assembler program. Machine language code, on the other hand, is the code that is executed directly by the computer's central processing unit. Additionally, an assembly program is sometimes used to refer to a set of instructions written in assembly language. Regardless of the synonym used, an assembler program remains a critical tool for software development at the system level.