Keywords And White space in C

Keywords

The following list shows the reserved words in C. These reserved words may not be used as constant or variable or any other identifier names.

auto	else	long	switch
break	enum	register	typedef
case	extern	return	union
char	float	short	unsigned
const	for	signed	void
continue	goto	sizeof	volatile
default	if	static	while
do	int	struct	_Packed
double

White space 

A line containing only white space, possibly with a comment, is known as a blank line, and a C compiler totally ignores it.

White space is the term used in C to describe blanks, tabs, newline characters and comments. White space separates one part of a statement from another and enables the compiler to identify where one element in a statement, such as int, ends and the next element begins. Therefore, in the following statement:

int age;

There must be at least one white space character (usually a space) between int and age for the compiler to be able to distinguish them. On the other hand, in the following statement:

fruit = apples + oranges;   // get the total fruit

No white space characters are necessary between fruit and =, or between = and apples, although you are free to include some if you wish for readability purpose.