The direction of a correlation is either positive or negative. In a negative correlation, the variables move in inverse, or opposite, directions. In other words, as one variable increases, the other variable decreases. For example, there is a negative correlation between self-esteem and depression. In other words, the higher your self-esteem, the lower your feelings of depression.
Excel Communications was founded in 1988 by Dallas entrepreneur Kenny Troutt as a long distance reseller in the US telecom sector at the birth of telecom deregulation.
Microsoft originally marketed a spreadsheet program called Multiplan in 1982, which was very popular on CP/M systems, but on MS-DOS systems it lost popularity to Lotus 1-2-3. This promoted development of a new spreadsheet called Excel which started with the intention to 'do everything 1-2-3 does and do it better'. The first version of Excel was released for the Mac in 1985 and the first Windows version was released in November 1987. Lotus was slow to bring 1-2-3 to Windows and by 1988 Excel had started to outsell 1-2-3 and helped Microsoft achieve the position of leading PC software developer.