Avoid the use of numerical values or "magic numbers" in code when possible. Appropriately named symbolic constants clarify the intent of the programmer. In addition, if a specific number needs to be changed reassigning a symbolic value is much easier than replacing a specific number in the code because each case has to be checked specifically.
Non Compliant Code Example
if (age >= 18) {
takevote(personID);
}
...
if (age <= 18) {
checkSchoolEnrollment(personID);
}
Compliant Solution
enum { ADULT_AGE=18 };
...
if (age >= ADULT_AGE) {
takevote(personID);
}
...
if (age <= ADULT_AGE) {
checkSchoolEnrollment(personID);
}
In the compliant code it is easy to check if the user is an adult and process accordingly. If the definition of adult changes during iterations of the codebase it is much simpler to replace the value for ADULT_AGE in one place then search for instance of 18 and see if they're appropriate for change.
When declaring immutable symbolic values such as ADULT_AGE it is best to use const or enum as explained in
DCL00-A. Declare immutable values using const or enum
Risk Assessment
Mistakes regarding numeric values can cause unintended consequences if changes are not made uniformly
Rule |
Severity |
Likelihood |
Remediation Cost |
Priority |
Level |
|---|---|---|---|---|---|
EXP00-A |
1 (low) |
1(unlikely) |
2 (medium) |
P2 |
L3 |
References
Source: http://www.doc.ic.ac.uk/lab/cplus/c++.rules/chap10.html