High Level language is machine independent and assembly language though it is machine dependent yet mnemonics that are being used to represent instructions are not directly understandable by machine. Hence to make the machine understand the instructions provided by both the languages.
Compiler and Assembler are required to convert these instructions into machine language.
Compiler.
The software (set of programs) that reads a program written in high level language and translates it into an equivalent program in machine language is called as Compiler.
The program written by the programmer in high level language is called source program and the program generated by the compiler after translation is called as object program.
Compiler
Assembler.
The software (set of programs) that reads a program written in assembly language and translates it into an equivalent program in machine language is called as Assembler.
Assembler