ct6

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

.NH
Initialization of Variables
.PP
An external variable may be initialized at compile time
by following its name with an initializing value
when it is defined.
The initializing value has to be something whose value is known at compile time,
like a constant.
.E1
int	x	0;	/\** "0" could be any constant \**/
int	a	'a';
char	flag	0177;
int	\**p	&y[1];	/\** p now points to y[1] \**/
.E2
An external array can be initialized by following its name with
a list of initializations enclosed in braces:
.E1
int	x[4]	{0,1,2,3};		/\** makes x[i] = i \**/
int	y[ ]	{0,1,2,3};		/\** makes y big enough for 4 values \**/
char	\**msg	"syntax error\\n";	/\** braces unnecessary here \**/
char \**keyword[ ]{
	"if",
	"else",
	"for",
	"while",
	"break",
	"continue",
	0
};
.E2
This last one is very useful _
it makes 
.UL keyword
an array of pointers to character strings,
with a zero at the end so we can identify the
last element easily.
A simple lookup routine could scan this until
it either finds a match or encounters a zero keyword pointer:
.E1
lookup(str)		/\** search for str in keyword[ ] \**/
   char \**str; {
	int i,j,r;
	for( i=0; keyword[i] != 0; i\*+) {
		for( j=0; (r=keyword[i][j]) \*= str[j] && r != '\\0'; j\*+ );
		if( r \*= str[j] )
			return(i);
	}
	return(-1);
}
.E2
.PP
Sorry _
neither local variables nor structures can be initialized.