A few computers were built using " writable microcode". Software to make pdf writable. Such a computer is sometimes called a writable instruction set computer or WISC.
In this design hard- wired logic, rather than storing the microcode in ROM , the microcode is stored in a RAM called a writable control store WCS. Gaaiho PDF Suite 4 is a collection of three standalone applications: Gaaiho Doc is an industrial- strength PDF editor Gaaiho PDF Converter creates PDFs directly from Office , other formats .
Many experimental prototype computers use writable control stores; there are also commercial machines.