c programming Input and Output Formatting strings

The main input routine in C programs is scanf and the main output routine is printf, both of which use a format string to control their behavior.
The following program listing shows some common uses:



 #include int main() { 
int n;  
float f; 
double d; 
char s[100]; 

/* input an integer */ 

 scanf("%d", &n); 
 /* print an integer, no formatting */ 

 printf("%d\n", n); 
 /* print an integer, padded on left with spaces to total 6 chars */ 

 printf("%6d\n", n);

 /* print an integer, padded on right with spaces to total 6 chars */

 printf("%-6d\n", n); 

 /* print an integer, padded on left with zeroes to total 6 chars */

 printf("%.6d\n", n); 

/* input a string (whitespace delineated) */

 scanf("%s", s); 

  /* print a string, no formatting */

 printf("%s\n", s); 

 /* print a string, padded with spaces on left to 20 chars */

 printf("%20s\n", s);

 /* print a string, padded with spaces on right to 20 chars */

 printf("%-20s\n", s);

 /* print a string, truncated after 3 chars */

 printf("%.3s\n", s); 

  /* input a single precision floating point number */

 scanf("%f", &f); 

 /* print a float, default precision is 6 places */

 printf("%f\n", f);

  /* input a double precision floating point number */

 scanf("%lf", &d);

 /* print a double, default precision is 6 places */

 printf("%f\n", d); 

 /* print a double, 2 places of precision */

 printf("%.2f\n", d);

/* print a double, 2 places of precision, padded with space to 10 */

 printf("%10.2f\n", d);

 /* print a double, use exponential notation if more than 3 digits */

 printf("%.3g\n", d); 

}