Development The Use Of %D In C Programming

Hey Everybody,

I am new to all this and learning C from 'The C Programming Language' by Brian Kernighan which I picked up on Amazon. I am really enjoying it and often find myself loosing track of time.

I have had some experience with programming but nothing too serious, only the odd experiment with PHP to create some simple websites.

I wondered if someone could explain this for me, a beginner to understand.

Code:

#include <stdio.h>
int power(int m, int n);
  /* test power function */
  main()
  {
    int i;
    for (i = 0; i < 10; ++i)
      printf("%d %d %d\n", i, power(2,i), power(-3,i));
    return 0;
  }

  /* power: raise base to n-th power; n >= 0 */
  int power(int base, int n)
  {
    int i, p;
    p = 1;
    for (i = 1; i <= n; ++i)
      p = p * base;
    return p;
  }

This is a extract from the book, could someone please explain this following line of code:

Code:

printf("%d %d %d\n", i, power(2,i), power(-3,i));

I understand that I am using the 'printf()' function to display the result of 'power()'. However, I don't under the stand the use of '%d' and how this effects the result. Is this like introducing integer results which 'printf()' can use within the function?

I have also seen variations of the above, such as '%6d', '%6.2' etc..

I tried a quick google search, but didn't really fully understand what it was they were trying to describe.

Thanks in Advance,

Ashley

 

printf is used to 'inject' variables into strings. it is a better than concatenating variables to strings as it enables far easier centralization of text within a program. The %'s tell printf where the variables should be placed. %d means the input should be a number, %s means it should be a string. It is important to use the appropriate % other wise printf will try and interpreter numbers as letters and visa versa.

http://www.cplusplus.com/reference/clibrary/cstdio/printf/

 

Thanks for your reply. I found this useful and will look at the link which you sent. That appears like a useful resource so will add it to my bookmarks!