PPT Slide
= introduced as a sign for equality by Robert Recorde (1510-1558). He chose = because nothing could be more equal than two parallel lines. = for equality has been a worldwide convention for over 100 years.
The use of = for assignment was started in FORTRAN in the early 1950s. C (about 1970) and then C++ (1980s) continued to use = for assignment and introduced == for equality; thus bringing great confusion.
This use of = for assignment and requirement of == for equality has caused more confusion and waste of time in the whole world than any other notational convention.
Algol 60 used := for assignment, = for equality