NULL TERMINATOR

∙ '\0' is the null terminator.
∙ It is an unprintable character.
∙ It goes right after the last character in a string, in memory.
∙ Do not print the null terminator.
∙ Null terminator only exists in memory, not in files.
∙ Any string literal (e.g., "ABC") implies the null terminator.
  ∘ s2 and s3 are both arrays of 4 characters (not 3).
∙ Null terminator tells C functions that work with strings when they have 
  reached the end.
  ∘ Without it they will go on reading into other memory that they shouldn't touch.
∙ If you accidentally print '\0' to the terminal, you won't see anything.
  ∘ If you redirect the output to a file and open in Vim, you will ^@ for the
    null terminator.

'\n' is an escape code for the newline character (ASCII value 10 or 0x0a).
Escape codes take 2 characters in your C code, but result in 1 character in memory.
'\n' is 1 character in memory.
Same is true for '\"' or '\0' or '\\'.

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HOW TO CHECK IF YOUR CODE IS ACCIDENTALLY PRINTING THE NULL TERMINATOR ('\0')

$ vim c.actual.txt
#  You will see ^@ for the null terminator if present.

$ gcc  c.c  -o c

$ ./c > c.actual.txt

$ xxd  -g1  c.actual.txt
0000000: 41 42 43 00 0a                                   ABC..
                  ▲
            ┌─────┘
# The 00 above indicates that the null terminator ('\0') was in the c.actual.txt file,
# and thus was printed by the program.  (0a is the '\n'.)

$ ./c  |  xxd  -g1
0000000: 41 42 43 00 0a                                   ABC..
                  ▲
            ┌─────┘
# The 00 above indicates that the null terminator ('\0') was printed when we ran ./c.

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VARIADIC FUNCTIONS

1. Create a variable of type va_list.  Name should be like more_args (or similar).
   va_list more_args;

2. Call va_start(…) to initialize more_args.
   va_start(more_args, ███);  // where ███ is the name of the parameter just before ... in the
                              // function signature

3. Use va_arg(…) to access ONE additional argument.
   … = va_arg(more_args, ███); // where ███ is the type of the argument you expect to find.
                                 // For example, if you expect to find an int, you might have
                                 // int next_int_arg = va_arg(more_args, int);
4. Call va_end(…) to finalize.
   va_end(more_args);

⚠ You can only access the additional arguments in order.

⚠ Variadic arguments are not stored in an array.

⚠ Do not call va_arg(…) too many times.