Compilation and Execution of C programs

There are different phases through which our program passes before being transformed into an executable form. The following figure shows these phases –

Let us take one  example program : onsettechie.c

Preprocessor:

            The source code is the code that we write using any text editor and the source code file is given an extension ‘.c’. This source code is firstly passed through the preprocessor. The preprocessor expands this code and passes it to the compiler.

                                        gcc -E onsettechie.c -o onsettechie.i

Compiler :

            The expanded code is passed to the compiler. The compiler converts this code into machine’s assembly language code.

                                       gcc -S onsettechie.i -o onsettechie.s

Assembler:

            This assembly language code is converted to object code by the system’s assembler. The name of the object file is same as that of source file. The extension in UNIX is ‘.o’.

                                       gcc -c onsettechie.s -o onsettechie.o

Linker:

            All programs written in C, use library functions. Library functions are precompiled and their object code is stored in library files with ‘.lib’ ( or ‘.a’) extension. The linker combines both the object code of library functions with the object code of our program. The output of the linker is executable file. In UNIX name is a.out or other name with -o option.

                                       gcc -E onsettechie.o -o onsettechie

Here you get little bit confusion go forward then you understand about about all these files.

onsettechie.c is source code.

onsettechie.i  is expanded code.

onsettechie.s is Assembly code.

onsettechie.o is Object code.

onsettechie    is binary executable.
you can these codes by using Vim editor.

Author : ManiKanta

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