> **1.** Section 15.1 listed several advantages of dividing a program into multiple source files.(a). Describe several other advantages

> (b). Describe some disadvantages

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> **2.** Which of the following should *not* be put in a header file? Why not?

b. Function definitions - Functions should only be defined once, and this allows multiple files to share the same function definition

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> **3.** We saw that writing `#include <file>` instead of `#include "file"` may not work if file is one that we've written. Would there be any problem with writing `$include "file"` instead of `#include <file>` if *file* is a system header?

Yes, `""` is a path relative to the current file, whereas `<>` is a path to the system's standard library headers.

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> **4.** Assume that `debug.h` is a header file with the following contents...
>(a). What is the output when the program is executed?

```
Output if DEBUG is defined:
Value of i: 1
Value of j: 2
Value of i + j: 3
Value of 2 * i + j - k: 1
```

> (b). What is the output if the `#define` directive is removed from `testdebug.c`?

```
Output if DEBUG is not defined:
```

> (c). Explain why the output is different in parts (a) and (b)

When `DEBUG` is defined, any instances of the `PRINT_DEBUG` token are replaced with a `printf` call during compile time, but when it's not defined, they're replaced with nothing.

> (d). Is it necessary for the `DEBUG` macro to be defined *before* `debug.h` is included in order for `PRINT_DEBUG` to have the desired effect? Justify your answer.

Macro invocations are evaluated sequentially, and so if `DEBUG` was defined after `PRINT_DEBUG`, then any usages of `PRINT_EVALUATION` would be have like `DEBUG` was not defined.