[SOLVED] Learning programming

markush · 07-06-2011, 03:01 PM

A syntaxerror in a.out makes no sense to me.

Could you do what someone recommended in a post above and (provided your program is called nabeel.c)

Code:

make nabeel

or as usual

Code:

gcc -o nabeel nabeel.c

and then try to execute the program

Code:

./nabeel

Markus

MTK358 · 07-06-2011, 03:15 PM

Also, I recommend that you use "int main()" instead of "void main()". "void main()" is actually wrong, even though some compilers support it.

Nabeel · 07-06-2011, 10:45 PM

The gcc command worked and the program executed
Thanks

MTK358 · 07-07-2011, 08:21 AM

Quote:

Originally Posted by Nabeel

The gcc command worked and the program executed
Thanks

Good, but I wanted to say something:

In another thread, you tried to execute C code using the shell. Did you try running the executable like this:

Code:

sh a.out

? That clearly won't work, because compiled code is machine code that runs on the CPU, not a bunch of shell commands. The shell doesn't run stuff (other than shell scripts), the kernel does.

I see that it's a common misconception that the shell is somehow strongly integrated into the OS, and that's simply wrong. It's just another program, there's nothing special about it. All it does is both provide an interactive environment that lets you easily run other programs, and let you automate things by putting the commands in a file instead of typing them interactively.

markush · 07-07-2011, 08:53 AM

Quote:

Originally Posted by MTK358

...

Code:

sh a.out

...

Yes, this would make sense as an explanation.

@Nabeel: be sure to read the manuals! There are many tutorials in the internet, about C, about Linux in general, the Shell and many more.

Markus

pafoo · 07-08-2011, 10:50 PM

*chant* python! python! python!

Atleast it will teach you to indent =) A skill alot of programmers lack lol

TobiSGD · 07-11-2011, 04:53 AM

Spam, reported.

Nabeel · 07-12-2011, 11:51 PM

Hi
When I compile a program, The compiler throws out a binary file. SO my Question is "Can I take this binary file to any other PC and Run it there, Provided that, the new machine is a windows or linux based pc"????

markush · 07-13-2011, 12:21 AM

It will run on a Linux-PC only.

If you have a 32bit Linux your program will run on any 32bit Linux-PC. 64bit respectively, but it is possible to run 32bit-programs on 64bit-systems when one has a multilib-environment.

Long story short: programs for Linux will only run on Linux. Programs for Windows will only run on Windows.

There are some exceptions: Java-programs run inside a virtual-machine and are independent of the operatingsystem. And Scripting-languages are not compiled but have an interpreter, so they are also independent of the OS.

Markus

b0uncer · 07-13-2011, 02:57 AM

Quote:

Originally Posted by Nabeel

Hi
When I compile a program, The compiler throws out a binary file. SO my Question is "Can I take this binary file to any other PC and Run it there, Provided that, the new machine is a windows or linux based pc"????

Quote:

Originally Posted by markush

It will run on a Linux-PC only.

If you have a 32bit Linux your program will run on any 32bit Linux-PC. 64bit respectively, but it is possible to run 32bit-programs on 64bit-systems when one has a multilib-environment.

Long story short: programs for Linux will only run on Linux. Programs for Windows will only run on Windows.

There are some exceptions: Java-programs run inside a virtual-machine and are independent of the operatingsystem. And Scripting-languages are not compiled but have an interpreter, so they are also independent of the OS.

Markus

Clarification: if may run on other Linux systems (if you compiled it under Linux), provided that the environments are similar. For example if the program uses libraries that are not present on the other system, then it won't run. If you're careful enough, there are good chances that it will. And if you write your code not to depend on any external libraries that are operating system specific, you can expect to be able to compile your code on Linux and Windows alike; typically, though, programs use system-specific libraries which means they cannot be "just compiled" on another OS (say, Linux -> Windows) and have it work. In such cases those "dependencies" have to be modified to work on the other system before compilation.

Telemachos · 07-13-2011, 08:12 AM

This is maybe a minor point maybe, but you should not be writing void main() in modern C code. It should be more like this:

Code:

int main(void) {
    # Do whatever
    
    # Later, perhaps much later...
    return 0;
}

There are other more complex forms of that, but that's a simple start.

See the following for discussion:

Nabeel · 07-25-2011, 02:58 PM

I had wrote and compiled this program tonight, although it got compiled but gave"segmentation fault" in its execution

Here is the program

Code:

#include <stdio.h>

int main(void)
{
	int age;
	char gender;
	char name[10]=("\0");
	char class[4]=("\0");
	
	printf("Input your name \n");
	scanf("%s",name);
	printf("Input your Course Name \n");
	scanf("%s",class);
	printf("YOUR AGE???? \n");
	scanf("%d",age);
	printf("Gender \n");
	scanf("%s",gender);
printf("Your Name is %s",name);
printf("You are studying in %s",class);
printf("Your gender is %s",gender);
printf("and you are %d years old",age);

getchar();


}

And this is the error

Code:

Input your name 
Nabeel
Input your Course Name 
BSc
YOUR AGE???? 
18
Gender 
m
Segmentation fault

MTK358 · 07-25-2011, 03:29 PM

Do you understand that a char is different from a char[]?

ta0kira · 07-25-2011, 03:49 PM

Quote:

Originally Posted by b0uncer

...
For example if the program uses libraries that are not present on the other system, then it won't run. If you're careful enough, there are good chances that it will.
...

This all depends on the sonames of the libraries you link to, which are generally associated with the major and minor release of the library. This means most binaries that link to even just libc might not work on a different release of the same distribution. With gcc, the default options will cause linking to at least libc; you have to go out of your way to have no run-time dependencies.

In general, you should assume that a compiled program will at best only work on the exact version of the distribution you compiled it on. This is why compiled software packages are usually specific to single versions of a distribution.
Kevin Barry

pielas · 07-26-2011, 12:56 AM

You should use scanf("%d",&age) instead of scanf("%d",age) and scanf("%s",&gender) instead of scanf("%s",gender).