casio fx-4000p

the more modern wallet style casio programmable. it uses formula entry rather than direct calculation, hence the ans button.

this was one of the first machines to make use of a newer programming style based around writing expressions. its actually quite good once you get used to it. you get all the proper stuff like conditional jumps, loops like isz, dsz, labels and subroutines. some of the graphic machines like the fx-7000g also programmed the same way.

however, some similar looking models like the fx-5000f had evolved the idea of formula execution to the point where casio removed the ability to create loops and perform conditional jumps. unfortunately, this makes true programming impossible.