Simply assembly is the lenguage of the PC, at the lower level. To write a function in higher level as C++ or basic you have to follow the specified sintax as open-close parentesis, declare variables and then you are ready to start. In assebly there isn't this, or better, there is, but it is not so clear: you can call a routine using CALL and the routine ends with RET. But it is not so simple: first you have to understand at least how use ALL the registries of the processor, and how the memory is used (POP PUSH). Then you will find that you can simply translate every C++/basic function line per line, simply expanding every line to a lot a instructions. This will require a lot of timem so ... it only depends on what you have to prepare or why. It is also possible to insert some lines of assembly in a C++ function using asm__, in this way you have only to prepare a short function to do what you need. :-D
Russell