Best practices of working with data types

Numbers in General

• Avoid “magic numbers” Magic numbers are literal numbers, such as 100 or 47524, that appear in the middle of a program without explanation.

• Use hard-coded 0s and 1s if you need to

• Anticipate divide-by-zero errors

• Make type conversions obvious

• Heed your compiler’s warnings

Floating-Point Numbers

• Avoid additions and subtractions on numbers that have greatly different magnitudes With a 32-bit floating-point variable, 1,000,000.00 + 0.1 probably produces an answer of 1,000,000.00 because 32 bits don’t give you enough significant digits to encompass the range between 1,000,000 and 0.1.

• Avoid equality comparisons

• Anticipate rounding errors

Characters and Strings

• Avoid magic characters and strings

• Watch for off-by-one errors Because substrings can be indexed much as arrays are, watch for off-by-one errors that read or write past the end of a string.

• Decide on an internationalization/localization strategy early in the lifetime of a program

• If you know you only need to support a single alphabetic language, consider using an ISO 8859 character set

• If you need to support multiple languages, use Unicode

Boolean Variables

• Use boolean variables to document your program Instead of merely testing a boolean expression, you can assign the expression to a variable that makes the implication of the test unmistakable.

• Use boolean variables to simplify complicated tests

Enumerated Types

• Use enumerated types for readability

• Use enumerated types for reliability

• Use enumerated types for modifiability

• Use enumerated types as an alternative to boolean variables

• Check for invalid values

Integers

• Check for integer division (the integer division (7/10) equals 0)

• Check for integer overflow

• Check for overflow in intermediate results