MathPad uses a text window rather than simulating buttons on a hand held calculator.
This live scratchpad interface allows you to see and edit your entire calculation. Formulas can be entered directly and different values can be plugged in for easy "what if" calculating. In addition to being a handy little calculator, MathPad can also take on larger problems. Simple plotting allows quick visualization of results. General purpose arrays allow calculations involving vectors, complex numbers, matrix algebra, etc... 2D arrays can be displayed as grayscale or color images. MathPad does not have all the features of high-end commercial programs such as Mathematica, but it can handle fairly sophisticated numerical problems with a much smaller memory requirement (190K).
MathPad 2.4 runs on a Mac with a 68020 or better (including PowerPC native). System 7.0 or better is required. A 68000 version is also available.