Programming Tutorials

Formatting with printf in C

By: Siva  

We could right justify our output using the format specifiers. The field-width specifier tells printf( ) how many columns on screen should be used while printing a value(as in %wd),here the value is right justified and is padded with blanks on the left. If we include the minus sign in format specifier (as in %-wd), this means left justification is desired and the value will be padded with blanks on the right. 

Eg:- main()

{

int a,b;
a=2134;
b=2756;
printf(“%5d /n”,a);
printf(“%-5d /n”,b);

}

The output for “a” would be as

        2     1     3    4 

-  -  -  -  - 

The output for “b” would be as

2 7 5 6

-  -  -  -  - 
 
For float data type the format is % t.nf where ‘t’ denotes the total width and ‘n’ the number of decimal spaces. For example 

main()

{

float x,y;
x= 3.141592;
y=14.4;
printf(“%6.3f \n”,x);
printf(“%-5.2f \n”,y);

} 
 

The output for ‘x’ would be as

  3 . 1 4 2

- - - - - - 

The output for ‘y’ would be as

1 4 . 4 0

- - - - -

Similarly, for formatting a string %ds is used. For example, %10s ,%25s etc. The string could also be formatted using a decimal value, as in %5.3s. Here it specifies how many characters are to be printed. 

Example:

main()

{

char text1[ ] = “Hello”;

char text2[ ] =  “World”;

printf(“% 10s \n,text1);

printf(“%5.3s \n,text2);

printf(“%-5.3s,text2);

} 

The output for text1 would be as

          H e l l o

- - - - - - - - - -  

The output for text2 would be as

    w o r

- - - - - 

The output for text2 would be as

w o r

- - - - - 
 

Special Control Characters

Control characters are invisible on the screen. They have special purposes usually to do with cursor movement. They are written into an ordinary string by typing a backslash character \ followed by some other character. These characters are listed below.