[BTPH]

okay im doing some calculations and i need my numbers rounded to 2 decimal places, im using C.

if defined all my values as doubles and im using %lf for all the scanf'sa and printf's but it goes to too many decimal places, i remember something about putting a number (say 6.2) in between the % (%6.2lf) but i dont want to restric the high numbers, just the decimals, how can i do this?

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here's some rounding code to play with.

using %6.2 does not restrict a large number. the 6 means display at least 6 digits(including the decimal point and 2 digits after the decimal point). experiment - try %12.5, %3.0, ...

void decimals_2(  ) {
  double d = 1234.5678;
  double rounded = 0.0;

  printf("%lf \n", d );                /* show entire double */
  printf("rounded?    %6.2lf \n", d ); /* appears to be rounded */
  printf("not rounded %6.3lf \n", d ); /* but it isn't */

  /* 
	d * 100.0 shift decimal 2 places right
    + 0.5     for rounding
	(int)     cast to int 
  */
  int n = (int)( d * 100.0 + 0.5 );

  /* shift decimal 2 places left */
  rounded = n / 100.0;
  
  /* use %6.2 to show only 2 decimal places */
  printf("rounded?    %6.2lf \n", rounded );

  /* use %6.3 to verify rounding */
  printf("yes         %6.3lf \n", rounded );
}

[bdlt]

here's some rounding code to play with.

using %6.2 does not restrict a large number. the 6 means display at least 6 digits(including the decimal point and 2 digits after the decimal point). experiment - try %12.5, %3.0, ...

void decimals_2(  ) {
  double d = 1234.5678;
  double rounded = 0.0;

  printf("%lf \n", d );                /* show entire double */
  printf("rounded?    %6.2lf \n", d ); /* appears to be rounded */
  printf("not rounded %6.3lf \n", d ); /* but it isn't */

  /* 
	d * 100.0 shift decimal 2 places right
    + 0.5     for rounding
	(int)     cast to int 
  */
  int n = (int)( d * 100.0 + 0.5 );

  /* shift decimal 2 places left */
  rounded = n / 100.0;
  
  /* use %6.2 to show only 2 decimal places */
  printf("rounded?    %6.2lf \n", rounded );

  /* use %6.3 to verify rounding */
  printf("yes         %6.3lf \n", rounded );
}