TRICKY "C" Questions

How do you write a program which produces its own source code as its output?
How can I find the day of the week given the date?
Why doesn’t C have nested functions?
What is the most efficient way to count the number of bits which are set in a value?
How can I convert integers to binary or hexadecimal?
How can I call a function, given its name as a string?
How do I access command-line arguments?
How can I return multiple values from a function?
How can I invoke another program from within a C program?
How can I access memory located at a certain address?
How can I allocate arrays or structures bigger than 64K?
How can I find out how much memory is available?
How can I read a directory in a C program?
How can I increase the allowable number of simultaneously open files?
What’s wrong with the call fopen(”c:\newdir\file.dat”, “r”)?