help with scanf, is this the most efficient way.

[DIY]

Is this the correct way to use scanf. And is there a more efficient way or is there another way that uses less memory. I know this is a very simple example but i'm just starting out. I want to learn to write correct, effiecient and portable code. BTW I am using Dev 4.0. Thanks for your input.


#include <stdio.h>
#include <stdlib.h>

int main()
{
int a = 0, b = 0;

scanf("%d %d", &a, &b);

printf("The numbers are %d and %d.\nThe sum is %d.\nThe differenceis %d.\nThe product is %d.\n\n", a, b, a + b, abs(a - b), abs(a * b));

system("PAUSE");
return 0;
}

[DIY]

Does putting the computation in the statement use less memory than asigning the computation to a variable?

printf("The numbers are %d and %d.\nThe sum is %d.\nThe differenceis %d.\nThe product is %d.\n\n", a, b, a + b, abs(a - b), abs(a * b));

[Unregistered]

You might want to prompt the user to make an input.

[DYI]

I understand that. It is just for an example.

[Unregistered]

I want to learn to write correct, effiecient and portable code.

That's why I pointed out the need to prompt the user.

Does putting the computation in the statement use less memory than asigning the computation to a variable?

It certainly makes your code harder to read.

The best way to write code is to present it in as simple a style as possible.

Your computations should be separate and distinct, so it becomes more intuitive to the unfamiliar reader.

[DIY]

I did not find it hard to read but I take note of your suggestion. I rewrote it and hope to have my original concerns addressed. Thank you for the advice.

[Prelude]

>Is this the correct way to use scanf.
Very close:

#include <stdio.h>
#include <stdlib.h>

int main ( void )
{
  int a = 0, b = 0;
  
  printf ( "Enter two numbers: " );
  /*
  ** Always check return values.
  */
  if ( scanf ( "%d %d", &a, &b ) == 2 ) {
    printf ( "A\tB\tSum\tDiff\tProd\n" );
    printf ( "%d\t%d\t%d\t%d\t%d\n",
      a, b, a + b, abs ( a - b ), abs ( a * b ) );
  }
  else
    perror ( "Invalid input" );
  /*
  ** system() is not very portable because it's
  ** argument is platform dependent. This works
  ** just as well.
  */
  printf ( "Press return to continue" );
  (void)getchar();
  /*
  ** When you include stdlib.h, it never hurts to
  ** use the EXIT_SUCCESS macro to improve readability.
  */
  return EXIT_SUCCESS;
}

>I want to learn to write correct, effiecient and portable code.
You will want to invest in several good books on C as well as the ISO C standard. Refer to them for everything until you are confident in your knowledge. Another excellent idea is to get a Lint program for C which will warn you about all kinds of subtle problems concerning syntax, semantics, portability, etc... My favorite Lint is LCLint/Split which can be found here. It takes some time to get used to so many warnings, but you'll find your code improves dramatically with regular Linting.

-Prelude

[Unregistered]

My mistake about the system call. I was just using it to keep the console open. Didn't know any other way to do it and I forgot to delete it before I posted.

So it is there is no need to assign a variable to the computation:

answer = a + b ;    //does this uses more memory? Or the same?
printf("%d", answer) ;

It is beter to:

printf("%d", a + b) ;

[DIY]

The more variables the more memory I guess. That makes sense.
Thanks for all the posts.

[Prelude]

>does this uses more memory?
It uses more, but in this day and age the increase is negligible so you should concentrate more on readability than memory usage and speed. There is a time for such optimizations, but not often for the average programmer. Use what you find easiest to read and most comfortable to write and those who maintain your code with thank you for it.

-Prelude

[mithrandir]

>> I want to learn to write correct, effiecient and portable code.<<

I know prelude has already brought this up, but I strongly discourage people from using a system calls. System calls reduce the efficiency of your program - the CPU time dedicated to a system call is considerable.