The software includes subjects like geometry, algebra, spreadsheets, graphing, statistics and calculus. KAlgebra uses an intuitive algebraic syntax, similar to those used on modern graphing calculators. Some graphing calculators have CAS features. Students are also expected to use graphing calculators with statistical capabilities. Maya Kosoff wrote about how teachers use DonorsChoose to fundraise for Texas Instruments graphing calculators. Many TI calculators are still sold without graphing capabilities. Games continue to be programmed on graphing calculators with increasing complexity. The application features such tools as a graphing calculator and a unit converter. The TI-83 series is a series of graphing calculators manufactured by Texas Instruments. The TI-92 series of graphing calculators are a line of calculators produced by Texas Instruments. There are five calculators in the 49/50 series of HP graphing calculators. Power Macintosh machines also included NuCalc, a graphing calculator. There are several companies that manufacture models of graphing calculators. Its larger size was also rather cumbersome compared to other graphing calculators. Such curve fitting functionality is often found in graphing software or spreadsheets.