Page History

Avoid the use of "magic numbers" ( in code when possible. Magic numbers are constant values that represent an arbitrary value, such as a determined appropriate buffer size, or a malleable concept such as the age a person is considered an adult, which could change in a different country) in code where it is possiblefrom one location to another. Rather, use appropriately named symbolic constants clarify the intent of the code. In addition, if a specific value needs to be changed reassigning a symbolic constant once is more efficient and less error prone then replacing every instance of the value to be changed.

...

enum { ADULT_AGE=18 };
/* ... */
if (age >= ADULT_AGE) {
   /* Take action */
}
else {
  /* Take a different action */
}
/* ... */

Compliant Solution

While replacing numeric constants with a symbolic constant is often a good practice, it can be taken too far. In this compliant solution, for example, the quadratic theorem is provably correct" with hardcoded constants that will never be changed.

x = (-b + sqrt(b*b - 4*a*c)) / (2*a);

Replacing numeric constants with symbolic constants in this example does nothing to improve the readability of the code, and may in fact make the code more difficult to read:

enum { TWO = 2 };     /* a scalar */
enum { FOUR = 4 };    /* a scalar */
enum { SQUARE = 2 };  /* an exponent */
x = (-b + sqrt(pow(b,SQUARE) - FOUR*a*c))/ (TWO * a);

When implementing recommendations it is always necessary to use sound judgment.

Risk Assessment

Using numeric literals makes code more difficult to read and understand.

...