rardin

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sbdsa

smeezekitty

with no libraries:
DOS = difficult.
LINUX = impossable.

anishakaul

I tried the following code as it is on suse 10.3 with the default gcc compilor! While compilation it gave a warning but still compiled without errors and gave the expected output !

int main ()
{
printf ("\nThank God !\n");
return 0;
}

Is this what u wanted ?

ghostdog74

bull. Its possible. And, its spelt "impossible".

smeezekitty

then show.

ghostdog74

ever heard of assembly?

Hko

This story comes close...

H_TeXMeX_H

You can probably write it using assembly. But, what a stupid interview question. When would you ever need to do this ? Goodness, how much dumber can they get.

All of a sudden the servers all crash, but one is left in a state of limbo, nothing works except gcc and nasm, but the standard libraries have been disabled/deleted. Your only hope is to use gcc or nasm to write a small program to say "hello world", thus telling everyone that everything is ok and not to panic.

ghostdog74

the point i am making is just to refute what smeezekitty said. In Linux, it is not impossible.

pcunix

I suspect that the point of the question is to probe creativity and general knowledge. When I was interviewing, I'd ask questions like this. The point wasn't to write such a program - what I wanted to hear was HOW you'd write it. Do you know the difference between a system call and a library call? Do you know what /dev/tty is?

And no, "That's dumb" wouldn't have been a good answer :-)

H_TeXMeX_H

Oh, well, but they didn't ask how. They asked you to do it.

I'm sure they could have come up with not only something better, but something meaningful.

pcunix

Not to be pedantic, but seeing a written program also answers "how" :-)

Interviewing is tough. A lot of people who really aren't worth hiring can answer the easy stuff. Stepping outside of comfort zones, even if unrealistic, can tell you a lot about a persons true abilities.

It's especially the case when you aren't necessarily looking for specific skills so much as general problem solver.

BTW, Google is famous for asking tough interview questions - sometimes very specific, but sometimes real flights of fancy.

rob.rice

format ELF executable 3
entry start

segment readable executable

start:

mov eax,4
mov ebx,1
mov ecx,msg
mov edx,msg_size
int 0x80

mov eax,1
xor ebx,ebx
int 0x80

segment readable writeable

msg db 'Hello world!',0xA
msg_size = $-msg

now that I have shown you how it's done
I leave it up to you to find the assembler this syntax works with

Sergei Steshenko

No, the question is not dumb, and there are real needs for things like that.

When I was much younger, I managed to understand how "C" runtime in Borland's Turbo-C was linked to 'main' and how to avoid the linking.

After that I managed to use that Turbo-C to write in "C" for bare metal (with bare minimum inline assembly). That was my job at the time - to write for bare metal. And I was using VGA memory directly for output, so even BIOS was bypassed. And it was actually interesting and useful - I used to "allocate" different screen areas (i.e. various areas in VGA memory) for different diagnostic messages, so I could effectively have a number of checkpoints in my program.

Furthermore, VGA memory was big enough for some small programs/tests - for example, I could test a potentially faulty RAM module - the memory test resided in that VGA memory in the page not currently displayed on screen.

From time to time I (still ?) see job ads with part of job description being programming for bare metal.

smeezekitty

Thats different, linux is a high level protected mode environment that you cannot just call interrupt 0x10 to do the printing.