The Gaussian symbol is a mathematical symbol in the form of square brackets[x] , indicating the largest integer not greater than (equal to or less than) the number x, that is, ${\displaystyle x-1<[x]\leq x}$.

The Gaussian symbol first appeared in Gaussian mathematics "Arithmetic Research".

Operation example:

${\displaystyle [\pi ]=3,[2]=2,\left[-{\frac {5}{2))\right]=-3}$。

In computer science, the Gaussian symbol is often expressed as the INT() function.

Later, in 1962, Kenneth Iverson called the Gaussian symbol in his book "A Programming Language" (${\displaystyle \lfloor x\rfloor }$，floor) and introduced it at the same time. Take the top symbol (${\displaystyle \lceil x\rceil }$，ceil) (used to represent the smallest of the integers not less than x).

• ${\displaystyle [x]\leq x<[x]+1}$

If and only if x is an integer, the equal sign on the left holds.

• For all real numbers x, there are:

${\displaystyle \left[{\frac {x}{2))\right]={\frac {1}{4))((-1)^{[x]}-1+2[x])}$

${\displaystyle \left[{\frac {x}{3))\right]={\frac {-2}{\sqrt {3))}\sin({\frac {2\pi }{3))[x]+{\frac {\pi }{3)))+1}$

• When n is a positive integer, there are:

${\displaystyle \left[{\frac {x}{n))\right]={\frac {x-x(rem~n)}{n))}$

• When x and n are positive numbers, there are:

${\displaystyle \left[{\frac {n}{x))\right]\geq {\frac {n}{x))-{\frac {x-1}{x))}$

• For any integer k and any real number x, there are:

${\displaystyle [x+k]=k+[x].}$

• If x is a real number and n is an integer, we have ${\displaystyle n\leq x}$ if and only if ${\displaystyle n\leq [x]}$.
• Using the Gaussian notation, many prime formulas can be generated (but have no practical use).
• For non-integer real numbers x, the Gaussian function has the following Fourier series expansion:

${\displaystyle [x]=x-{\frac {1}{2))+{\frac {1}{\pi ))\sum _{k=1}^{\infty }{\frac {\sin(2\pi kx)}{k)).}$

• If m and n are positive prime numbers that are relatively prime, then:

${\displaystyle \sum _{i=1}^{n-1}[im/n]=(m-1)(n-1)/2}$

• According to Beatty's theorem, every positive irrational number can be divided into a set of integers by Gaussian notation.
• For each positive integer k, the representation under p carry is  ${\displaystyle [\log _{p}(k)]+1}$  digit.