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Real Arithmetic in C

Real Arithmetic

The C language includes the basic real arithmetic operators.
The result of applying the real operators to reals is another real.
The same operators are used for real values as for integer values, except that the remainder (%) operator is not supported for real numbers.

A Program using real Arithmetic

Program listing

/***************************************************************
 * File:    rarith.c
 * Purpose: Program to report the results 
 *          of real arithmetic operations.
 * Author:  John Young
 * Date:    May 24, 2004
 ***************************************************************/

#include <stdio.h>

int main () {
  double Entry1;
  double Entry2;
  double Result;

  printf ("Enter a positive or negative real number: ");
  scanf ("%lf", &Entry1);
  printf ("Enter another positive or negative real number: ");
  scanf ("%lf", &Entry2);
  Result = Entry1 + Entry2;
  printf ("%lf + %lf = %lf\n", Entry1, Entry2, Result);
  Result = Entry1 - Entry2;
  printf ("%lf - %lf = %lf\n", Entry1, Entry2, Result);
  Result = Entry1 * Entry2;
  printf ("%lf * %lf = %lf\n", Entry1, Entry2, Result);
  Result = Entry1 / Entry2;
  printf ("%lf / %lf = %lf\n", Entry1, Entry2, Result);

  return 0;
}

Program output

Enter a positive or negative real number: 432.5
Enter another positive or negative real number: 11.9 
432.500000 + 11.900000 = 444.400000
432.500000 - 11.900000 = 420.600000
432.500000 * 11.900000 = 5146.750000
432.500000 / 11.900000 = 36.344538

This program will input two numbers from standard input, normally the keyboard, apply the real operators to the numbers, and then reports the results to standard output, normally the display screen.

Declarations

Real Variable Declaration

A real variable is declared with the keyword double followed by an identifier which will be the name of the variable.
Syntax:
double <name>;

Addition

The addition operator is the plus sign (+).
Addition of reals works as expected, unless the range of real values is exceeded (which is unlikely.)
Style: Programs are more readable if spaces are used before and after the addition operator.

Subtraction

The subtraction operator is the minus sign (-).
Addition of reals works as expected, unless the range of real values is exceeded (which is unlikely.)
Style: Programs are more readable if spaces are used before and after the subtraction operator.

Multiplication

The multiplication operator is the asterisk (*).
Multiplication of reals works as expected, unless the range of real values is exceeded (which is unlikely.)
Style: Programs are more readable if spaces are used before and after the multiplication operator.

Division

The division operator is the forward slash (/).
Division of reals works as expected, with the quotient being resolved to the precision limit of the computer, unless the range of real values is exceeded (which is unlikely.)
There is no remainder or remainder function for real division.
Style: Programs are more readable if spaces are used before and after the division operator.

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