At Hive Helsinki, a 42 Network school, students must write projects according to the "norme". Many formats are restricted, so the code may look surprising in some places.

The built-in C Library functions we are allowed to use for almost all of our projects are highly limited. Generally, we can only use the following:

• write
• malloc
• free
• exit

With such limited resources available, we must recode much of our own libraries. In particular, it's time we made our printf, which has an undeniable utility to a coder.

The versatility of the printf function in C represents a great exercise in programming for us. This project is of moderate difficulty. It will enable you to discover variadic functions in C in a particularly relevant context as well as learn about a great example of a basic “dispatcher” in C via the use of an array of function’s pointers.

printf is prototyped as:

int printf(const char *format, ...);

where format is a character string, and is composed of zero or more directives. The directives specify how subsequent optional arguments are converted for output.

The directives are: ordinary characters (not %), which are copied unchanged to the output stream; and conversion specifications, each of which results in fetching zero or more subsequent arguments.

The conversion specification is introduced with the character %, and ends with a conversion specifier. In between, there may be (in this order) zero or more flags, an optional minimum field width, an optional precision and an optional length modifier. The overall syntax is:

%[$][flags][width][.precision][length modifier]conversion