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In this code what is the role of the symbol %3d ? I know that % means refer to a variable.

This is the code:

#include <stdio.h>
int main(void)
    int t, i, num[3][4];
    for(t=0; t<3; ++t)
        for(i=0; i<4; ++i)
            num[t][i] = (t*4)+i+1;
    /* now print them out */
    for(t=0; t<3; ++t) {
        for(i=0; i<4; ++i)
            printf("%3d ", num[t][i]);
        printf("\n");
    return 0;
                Voted as duplicate to the above - we don't need a seperate "what does %Nd mean?" for every possible N.
– Georg Fritzsche
                May 10, 2010 at 20:32
% means "Print a variable here"
3 means "use at least 3 spaces to display, padding as needed"
d means "The variable will be an integer"
Putting these together, it means "Print an integer, taking minimum 3 spaces"
See http://www.cplusplus.com/reference/clibrary/cstdio/printf/ for more information
That is a format specifier to print a decimal number (d) in three (at least) digits (3).
From man printf:
  
An optional decimal digit string
  specifying a minimum field width.  If
  the converted value has fewer
  characters than the field width, it
  will be padded with spaces on the left
  (or right, if the left-adjustment flag
  has been given) to fill out the field
  width.
If X is 1234, it prints 1234.
If X is 123, it prints 123.
If X is 12, it prints _12 where _ is a leading single whitespace character.
If X is 1, it prints __1  where __ is two leading whitespacce characters.
You can specify the field width between the % and d(for decimal). It represents the total number of characters printed. 
A positive value, as mentioned in another answer, right-aligns the output and is the default. 
A negative value left-aligns the text.
example:
int a = 3;
printf("|%-3d|", a);
The output:
|3  |
You could also specify the field width as an additional parameter by using the * character:
int a = 3;
printf("|%*d|", 5, a);
which gives:
|    3|
                You are answering a quite old question which already has some well received answers. I can't see any added value in your answer. So, what's your reason of posting it?
– honk
                Oct 20, 2014 at 17:28
        
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