Compile the program in Example 6-1 (mem_segments.c), and list its size using ls -l. Although the program contains an array (mbuf) that is around 10 MB in size, the executable file is much smaller than this. Why is this?

Write a program to see what happens if we try to longjmp() into a function that has already returned.

Implement setenv() and unsetenv() using getenv(), putenv(), and, where necessary, code that directly modifies environ. Your version of unsetenv() should check to see whether there are multiple definitions of an environment variable, and remove them all (which is what the glibc version of unsetenv() does).