The number in a computer is expressed in binary, and the leftmost bit is generally used to indicate whether the number is positive or negative, so the number is a signed integer. If the leftmost bit is not used to represent positive or negative, but is connected with the following bits to represent an integer, then it is impossible to distinguish whether the number is positive or negative, and it can only be a positive number and an unsigned integer.

Chinese name: unsigned integer mbth: unsigned integer is often used to represent address, index and other attributes: introduction of positive integer, definition of unsigned integer in C language, introduction of two types of integers in computer: unsigned integer (also called unsigned integer), which must be positive integer; Signed integer, which can represent positive and negative integers. Unsigned integers are usually used to represent positive integers, such as addresses and indexes. They can be 8 bits, 16 bits, 32 bits, 64 bits or even more. The range of positive integers represented by 8-bit binary numbers is 0~255(-1), that represented by 16 bits is 0~65535(-1), and that represented by 32 bits is 0~-1. The difference between signed and unsigned int is signed and unsigned. They actually occupy the same number of bytes, but the signed one needs to arrange a place to represent the symbol of my value, so the absolute value it can represent is half less than that of the unsigned one. For example, if we have an integer of 1 byte (although this type does not exist), then the unsigned integer is as follows: 000000 ~1111/kloc-0. A byte is an 8-bit signed number. Because the first digit is used to represent the symbol, there are only 7 digits left to represent the number 000000 ~111,so it can also represent the range:-11. Define the classification of unsigned integers; Eger integer variable in C language: basic integer: int short integer: short integer; Long integer: Long int Add the modifier unsigned in the above three categories to specify that it is an unsigned number. If the modifier signed is added, specify "signed number"; If neither signed nor unsigned is specified, it means it is signed. The example is as follows: What is the output of the following code? Unsigned int a= 1, int b =-2; int c =-2； cout & lt& ltb & lt& ltendlif(a+c & gt； 0)cout & lt； & lta+b & lt； & ltendl Run Result: 4294967294 4294967295 Press any key to continue. First, the first line of the program, variables B and A are unsigned integers, which is a trap. Secondly, in a 32-bit system, the value range of int is-2147483648 ~+2147483647, while the value range of unsigned int is 0~4294967295. Negative numbers are represented by the complement of unsigned integers, so b is 4294967294. Third, int defaults to signed int. When using unsigned int operation, the result is converted into unsigned int, so a is 4294967295.