Everything can be written in assembler - if you have a few lifetimes.

Assembler code is the most effective code, but hard to maintain and error prone, as you practically type 1s and 0s (okay you actually use mnemonics like MOV, ADD, STOSB and stuff, but that does not really count).
Assembler code isn\'t suitable for big projects like PS, because when writing a program in assembler YOU (i.e. the programmer) have to take care of everything (load values from memory into CPU registers (not every register can do everything) instead of using variables, memory management, segmentation, blah blah plus the application almost instantly becomes non-portable to other platforms without putting a looo...ot of extra time into it.