GNU Compilation

• When a program is written, it is stored as a source program. The source program is a sequence of bytes that each represent a text character.
• Source programs in C have the .c extension
• Most source programs are encoded using the ASCII standard.
• The Compilation Process Steps

  1. Pre-processor
  2. Compiler
  3. Assembler
  4. Linker
• The preprocessor modifies the original source program into a modified source program. The modifications are specified by preprocessor directives that begin with #.
• Modified source programs have the .i extension instead of .c
• The compiler translates the modified source progrram into an assembly language program.
• The assembly language program consists of basic instructions that designate CPU register operations and the detailed execution of the program.
• Assembly programs (.s) are human readable.
• The assembler converts the assembly program into a relocatable object file.
• The relocatable object file is a binary file and not human readable. It also cannot be directly run until the linker resolves all conflicts.
• Object files are written as machine language and have the .o extension.
• The linker merges relocatable object files with shared object files and creates an executable object file that can be loaded up and run in the system.
• Static libraries are compiled into the application itself, while dynamic libraries are linked at runtime.
• A static library has the .a extension, while a dynamic library has the .so extension.
• Java, C, and Python are examples of high-level languages.
• Assembly language is specific to the processor architecture. RISC and CISC architectures have different instruction sets and thus, different encodings for their assembly programs.
• To translate a source program into an assembly program, use the command,

  gcc -S program.c
• To translate the assembly program to a machine program, use the command,

  gcc -c program.s