When programming, we store the variables in our computer’s memory, but the computer has to know what kind of data we want to store in them, since it is not going to occupy the same amount of memory to store a simple number than to store a single letter or a large number, and they are not going to be interpreted the same way.
The memory in our computers is organized in bytes. A byte is the minimum amount of memory that we can manage in C++. A byte can store a relatively small amount of data: one single character or a small integer (generally an integer between 0 and 255). In addition, the computer can manipulate more complex data types that come from grouping several bytes, such as long numbers or non-integer numbers.
Next you have a summary of the basic fundamental data types in C++, as well as the range of values that can be represented with each one:
| Name | Description | Size* | Range* |
|---|---|---|---|
char |
Character or small integer. | 1byte | signed: -128 to 127 unsigned: 0 to 255 |
short int (short) |
Short Integer. | 2bytes | signed: -32768 to 32767 unsigned: 0 to 65535 |
int |
Integer. | 4bytes | signed: -2147483648 to 2147483647 unsigned: 0 to 4294967295 |
long int (long) |
Long integer. | 4bytes | signed: -2147483648 to 2147483647 unsigned: 0 to 4294967295 |
bool |
Boolean value. It can take one of two values: true or false. | 1byte | true or false |
float |
Floating point number. | 4bytes | +/- 3.4e +/- 38 (~7 digits) |
double |
Double precision floating point number. | 8bytes | +/- 1.7e +/- 308 (~15 digits) |
long double |
Long double precision floating point number. | 8bytes | +/- 1.7e +/- 308 (~15 digits) |
wchar_t |
Wide character. | 2 or 4 bytes | 1 wide character |
* The values of the columns Size and Range depend on the system the program is compiled for. The values shown above are those found on most 32-bit systems. But for other systems, the general specification is that int has the natural size suggested by the system architecture (one “word”) and the four integer types char, short, int and long must each one be at least as large as the one preceding it, with char being always one byte in size. The same applies to the floating point types float, double and long double, where each one must provide at least as much precision as the preceding one.