Good Articles on Internals of C++ and Unix

"C a glorified assembler" or "C a generalized assembler"

Actually I only really started understanding C when I understood 2 things about it.
1) Anything you code in C finally translates to assembly language.
2) How your compiler interacts with the O.S. loading/linking mechanism.

A) C as a glorified assembler:
You can easily test this.
Use the 'gcc --save-temps ' feature of your gcc compiler to see the assembly language output.

C program to assembly code translation
>>>>>>>>
C program
>>>>>>>>extern int printf(const char *, ...)
int main()
{
 printf( "Hello, World!\n");
 return 0;
}
#Retain temporary intermediate files generated during preproc, compiling, assembling etc.
gcc --save-temps test.c

>>>>>>>>
Pseudo-Assembly (see link for more accurate example)
>>>>>>>>
.data                              # data section starts at say 0x100
msg ds "Hello, World!\n"           # define string with label as msg and content as "Hello, World!\n"

.text
push sp                            # save the current stack pointer
push msg                           # push the function parameter onto stack
call _printf                       # make the library call
ret   0                            # essentially return 0 as errorvalue to bash/cmd.exe

>>>>>>>>
Since the C language is portable from one platform to another it kind-of acts like a virtual machine (without byte-code generation of-course).
The same C program will compile on different machine-compiler pairs to the specific assembly language and O.S. of the platform in question.

This makes for  chip/hardware specific assembly(Intel x86 or Motorola or ARM ...) portability.

Refer:
C to Assembly Translation Article from EventHelix

B) Interaction with O.S. loader/linker/virtual-memory:
The specific C compiler would also link the O.S. specific C runtime properly.

So gcc which is a portable compiler would link in.
a) mingw C runtime on Win32
b) linux C runtime on Linux.

The same C program would also convert to correct assembly/runtime on
Watcom C++, Visual C++ compiler, AIX, HP/UX compilers etc.

Note:
a) printf() comes from the C Standard Library
b) C runtime library contains the startup code which executes before and after main

Refer:
1) C++ runtime environments on HP-UX
2) Internals of C/C++ compiler implementations
3) How to use debug C runtime to debug your application
4) How to write a minimal Kernel in C (a very simple Hello world program which also describes the libc C runtime library)
5) Understanding System Calls
Note:
The C standard library calls like open(), close(), putc(), getc() etc actually just forward the call to O.S. system calls in the linux kernel. The C runtime actually maps a stdlibrarycall to an interrupt vector i.e. system call index number in a lookup table. Then it uses a software interrupt to call the system call (transfers from user mode to kernel mode and back)

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These are a set of articles that take a look at what happens inside C, C++, Unix internals as we compile and run our programs. The info here is invaluable to debug compile errors, runtime errors and memory issues. You can go through these in your spare time. Take a print out to read in your spare time and go through these articles.

0.What Happens When You Compile and Link a Program
1.What a Compiler Turns Your C Code Into
2. Virtual Base Classes Implementation
3. How the C++ compiler mangles/decorates function names
4. Unix And C-C++ Runtime Memory Management For Programmers