data_types

Several of these types can be modified using the keywords signed, unsigned, short, and long. When one of these type modifiers is used by itself, a data type of int is assumed. A complete list of possible data types follows (equivalent types are displayed in the same row):

The size and range of any data type is compiler and architecture dependent. The “cfloat” (or “float.h”) header file often defines minimum and maximum values for the various data types. You can use the sizeof operator to determine the size of any data type (frequently expressed as a number of bytes). However, many architectures implement data types of a standard size. ints and floats are often 32-bit, chars 8-bit, and doubles are usually 64-bit. bools are often implemented as 8-bit data types. long long type is 64-bit.

Limits for numeric values are defined in the <limits> header. The templatized values of numeric_limits provide system-dependant numerical representations of the C++ data types. Use the appropriate function given the data type as the template argument as shown in the table below. Note that numeric_limits can be overloaded for user-defined types as well.

The most common usage is in bounds checking, to determine the minimum and maximum values a data type can hold. The following code prints out the minimum and maximum values for a short on the system it is run.

  #include <limits>
  std::cout << "Maximum short value: " << std::numeric_limits<short>::max() << std::endl;
  std::cout << "Minimum short value: " << std::numeric_limits<short>::min() << std::endl;

Simple type declarations are easy to understand:

  int i

However, it can be tricky to parse a more complicated type declarations:

  double **d[8]              // hmm...
  char *(*(**foo [][8])())[] // augh! what is foo?

To understand the above declarations, follow three rules:

1. Start at the variable name (d or foo in the examples above)
2. End with the data type (double or char above)
3. Go right when you can, and left when you must. (Grouping parentheses can cause you to bounce left.)

For example:

Another example:

For a much more detailed explanation, see Steve Friedl's excellent description of how to read C declarations at http://www.unixwiz.net/techtips/reading-cdecl.html.