Flags are fairly uncommon in format specifiers and although several flag options exist, you are most likely to use only two of them. The first is a minus sign (-), which you will use in conjunction with a field width specifier.

minus (-)

Consider the example given below, names are left justified and ages are right justified to names. To print name and age in a single line the format string of the prinf() could be "%15s %d".

Henry Jones 23

Sam Smith 14

The required code to print the name and age is given below:

#include<stdio.h>

int main(){

printf("%-15s %d\n","Henry Jones",23);

printf("%-15s %d","Sam Smith",14);

}

In the above code, 15 represents the width of the string and the - (minus) flag makes the string output to left justified and then age of the person gets printed in same line. Now consider the output as default right justified without using - (minus) flag in the formatted string of the printf.

~~~~Henry Jones 23

~~~~~~Sam Smith 14

The required code for default right justified as

#include<stdio.h>

int main(){

printf("%15s %d\n","Henry Jones",23);

printf("%15s %d","Sam Smith",14);

}

plus (+)

This flag is only meaningful with numeric data. By default, when printf displays a number, it prints a minus sign for negative numbers, but it does not print a plus sign for positive numbers. If you want the plus sign to appear, this flag will cause printf to display it.

#include<stdio.h>

int main(){

int num = 89;

int val = -34;

printf("%+d %+d",num, val);

}

Here + (plus) flag forces to print the sign of the number. For negative number it preceeds minus (-) sign before the number and for positive number the plus (+) signs preceeds the value. The above code produces the output as:

+89 -34

Space

It prints a blank space before the value, if value is negative then minus (-) sign is placed. Consider the example given below, where val is initialized with a positive value and num is initialized with a negative value

#include<stdio.h>

int main(){

int val = 34;

int num = -30;

printf("% d\n",val);//line1

printf("% d",num);//line2

}

The printf() at line1 inserted a space before the value of val and printf() at line2 prints the value of num without inserting an space. Because num have a negative value and the above code will produce the output as:

~34

-30

# (Hash)

It is used with o, x or X specifiers the value is preceeded with 0, 0x or 0X respectively for values different than zero. o is used as format specifier to convert a decimal number to its equivalent octal and x is used to prints its equivalent hexa-decimal number. Consider the example given below:

#include<stdio.h>

int main(){

int val = 14;

printf("%d in Octal = %#o\n",val,val);

printf("%d in hexadecimal (uppercase) = %#X\n",val,val);

printf("%d in hexadecimal = %#x",val,val);

}

The flag character # placed the appropriate format character before the equivalent octal and hexadecimal number as follows:

14 in Octal = 016

14 in hexadecimal (uppercase) = 0XE

14 in hexadecimal = 0xe

0 (Zero)

Left-pads the number with zeroes (0) instead of spaces when padding is specified with width sub-specifier. For example,

#include<stdio.h>

int main(){

int val = 14;

printf("%05d\n",val);//line1

printf("%5d",val);//line2

}

At line1 0 (zero) is padded before the value and 14 is displayed as right justified. Similarly at line2 14 get displayed as right justified, but instead of 0 padding blank spaces are padded before 14. In the above example, 5 is the size of the width specifier and the output of the code is as follows:

00014

1