An interpreter is a program which translates statements of a program into machine code.
It translates only one statement of the program at a time.
It reads only one statement of program, translates it and executes it.
Then it reads the next statement of the program again translates it and executes it. In this way it proceeds further till all the statements are translated and executed.
An interpreter reads only one line of a source program at a time and converts it to object codes.
After the C pre-processor has included all the header files and expanded all macros, the compiler can compile the program.
It does this by turning the C source code into an object code file, which is a file ending in .o which contains the binary version of the source code.
Object code is not directly executable, though. In order to make an executable, you also have to add code for all of the library functions that were #included into the file (this is not the same as including the declarations, which is what #include does).
It is a program which translates a high level language program into a machine language program.
A compiler is more intelligent than an assembler.
It checks all kinds of limits, ranges, errors etc. But its program run time is more and occupies a larger part of the memory.
It has slow speed. Because a compiler goes through the entire program and then translates the entire program into machine codes.