An unsigned int (unsigned integer) is the same as an int in that it stores a 4 byte integer value. However, Instead of storing both negative and positive numbers, an unsigned int can only store nonnegative values, yielding a range of 0 to 4,294,967,295 (the positive value is 2^32 - 1).
The difference between an unsigned int and a (signed) int lies in the way the highest bit, sometimes referred to as the “sign” bit, is interpreted. In the case of the Maple int type (which is signed), if the high bit is a “1”, the number is interpreted as a negative number, using a technique known as two’s complement math. The bits in an an unsigned int are interpreted according to the usual rules for converting binary to decimal.
An unsigned int is subject to the same overflow issues as a regular int; the only difference is that an unsigned int will “underflow” at 0, and “overflow” at 4,294,967,295. Here is some example code which illustrates this:
unsigned int x; x = 0; x--; // x now contains 4,294,967,295; rolled over "left to right" x++; // x now contains 0; rolled over "right to left"
The unsigned long type is a synonym for unsigned int.
Here is an example of declaring an unsigned int variable named pin, then giving it value 13:
unsigned int pin = 13;
The general syntax for declaring an unsigned int variable named var, then giving it value val, looks like:
unsigned int var = val;