Can I execute any c made prog without any os platform?

Question

I googled about it and somewhere I read ....

Yes, you can. That is happening in the case of embedded systems

I think NO, it\'s not poss

Answer 1

As an example: Building Bare-Metal ARM Systems with GNU

Many embedded systems do not have enough resources for a full OS, some may use a scheduler kernel or RTOS, others are coded 'bare metal'. The main() C entry point is entered after reset. Only a small amount of assembler code is required to initialise a microprocessor, to execute C code. All C requires to run generally is a stack - usually simply a case of initialising the stack pointer to a specific address. Some processor specific initialisation of interrupt/exception vectors, system clocks, memory controllers etc. may be necessary also.

On a desktop PC, typically you have a BIOS that handles basic hardware initialisation such as SDRAM controller setup and timing, and then bootstrapping from a disk boot-sector, which then in turn bootstraps an OS. Any of that code could be written in C (and some of it probably is), and it could do something other than boot an OS - it could do anything - it is just code.

OSs are useful for non-dedicated computing devices where the end user many select one of many programs to execute and possibly several simultaneously. Most embedded systems do just one thing, the software is often loaded from ROM or executes directly from ROM, and is never changed and executes indefinitely (usually stopped only by power-down).

You still of course might implement device drivers and the like, but often these are an integral part of the application rather than a separate entity. Even when you do use an RTOS in an embedded system, it is still generally integral to your application rather than an OS in the sense you might understand. In these cases the RTOS is simply a library like any other, and is often initialised and started from main() rather then the other way around as you might expect.

Answer 2

Obviously, you cannot execute any arbitrary C program without some sort of OS or OS-equivalent. Similarly, I can write a C program under Linux that won't run under Microsoft Windows.

However, you can write C programs on almost anything. It's a popular language to write software for embedded systems in, and they very often don't have an OS.

Many embedded systems have just a CPU hooked up to a ROM, with pins coming out of the chip that are directly attached to inputs and outputs. There is no user I/O, no file system, no process scheduling, nothing you'd typically want an OS for. In those cases, a C programmer might write a program that is burned into a ROM, which will handle everything itself.

(Some embedded systems are more complicated, and can use an OS. Linux is frequently used, since it's free for the use, can be made very compact, and can be changed at any level. Not all do, though.)

Answer 3

I think you would have fun writing 'toy' kernels that are designed to run under simulators like QEMU (or virtualization platforms, Xen + MiniOS is one of my favorites). With not (much) difficulty, you could get a basic console up and running and start printing things to it. Its really fun, educational and satisfying all at once.

If you are working on x86 .. and get your spiffy kernel working under QEMU .. there's a very good chance that it will also work on real hardware. You might enjoy it.

Anyway, the answer to your question is most decidedly yes. Its especially easier if you happen to be using a boot loader .. for instance, google memtest86 and grab the code.