The equal sign is one of the many characters that sites on our keyboards, but most people don’t know that the sign was actually invented–and not too long ago. The = sign was invented in 1557 by Robert Recorde. Prior to that people would literally write is equal to in their notes about the relationship between both sides of the equation.
Robert also championed the use of the + though he did not invent that symbol.
Today we recognize not only the = sign, but several deviations from it. The links below can help to shed some more light on this versatile keyboard addition.