Programs don’t need any of these unless output is needed. The language syntax includes Arabic numerals which produce integral values. The REPL knows how to print only integers and three functions to deal with numbers are provided. In each N is an expression that evaluates to an integer n.
(iN) yields n+1.
(dN) yields n−1.
(zN) yields K if n=0 and H otherwise.
(PN) yields n and causes the unicode character at code point n to be printed. (Optional at system build time.)
Values H = (λxy.y) and K = (λxy.x) are also primordial in order that z may yield them.