I'm a newbie to 80386 assembly language. Currently struggling on a school assignment that asks to write a function in assembly language that will be called in a c program.

extern int count(char *string, char c);

I think I have a sense of how this should be done, but still struggling with choosing the right instruction(instruction ends with 'b', 'w' or 'l') and perhaps the "right" register, I know there are some that are reserved to certain purposes.

.text
.global count

count:
    pushl