Formatting spacing with the printf function C

Question

How can I create a code where the spacing of the of the Numbers and Months is equidistant from one another. The code source code has been gotten in the answer of issue.

#include <stdio.h>

#define MAX_LEN 32

int main() {
    int Numbers[12] = {3, 4, 5, 1, 2, 7, 8, 9, 3, 4, 7, 8};
    char Months[][MAX_LEN] = {"Jan",       "Feb",     "March",    "April",
                              "May",       "June",    "July",     "August",
                              "September", "October", "November", "December"};

    for (int i = 0; i < 12; i++)
        printf("%s: %d\n", Months[i], Numbers[i]);

    return 0;
}

Output

Jan: 3
Feb: 4
March: 5
April: 1
May: 2
June: 7
July: 8
August: 9
September: 3
October: 4
November: 7
December: 8

Expected Output:

Jan:       3
Feb:       4
March:     5
April:     1
May:       2
June:      7
July:      8
August:    9
September: 3
October:   4
November:  7
December:  8

Answer 1

You can use extra modifiers in your format string to make printf() align things correctly:

• To print something of a particular width prepend the the width as an integer before the formatting character: e.g., %10s will print a string to a (maximum) column of width 10, padding to the left with spaces. If your string is longer than 10 characters, it prints the full string though so bear this in mind. So your particular example:

char Months[][MAX_LEN] = {"Jan",       "Feb",     "March",    "April",
                          "May",       "June",    "July",     "August",
                          "September", "October", "November", "December"};

for (int i = 0; i < 12; i++) {
  /* Note the 10 here! */
  printf("%10s: %d\n", Months[i], Numbers[i]);       
}

Results in

       Jan: 3
       Feb: 4
     March: 5
     April: 1
       May: 2
      June: 7
      July: 8
    August: 9
 September: 3
   October: 4
  November: 7
  December: 8

If you want to left-justify your strings, you simple prepend a - before the integer value, i.e.:

printf("%-10s: %d\n", Months[i], Numbers[i]);

Which produces

Jan       : 3
Feb       : 4
March     : 5
April     : 1
May       : 2
June      : 7
July      : 8
August    : 9
September : 3
October   : 4
November  : 7
December  : 8

• Alternatively you can also use the * which allows you to state the length to pad to variably in the printf() call. To use it you calculate the length you wish to pad to as an extra argument:

int myPadWidth = 15;
/* calculate the length of Months[i] each loop and cast size_t result to int */
int lenMonths = (int)strlen(Months[i]);
/* Note the extra argument in the printf call here! */
printf("%s: %*d\n",Months[i],myPadWidth-lenMonths,Numbers[i]);

Which would result in

Jan:            3
Feb:            4
March:          5
April:          1
May:            2
June:           7
July:           8
August:         9
September:      3
October:        4
November:       7
December:       8