Program Structure/Functions

type fnc(type1,: : : )	function declarations
type name external variable declarations
main() {            main routine

    declarations       local variable declarations
    statements
}

type fnc(arg1,...) {        function defnition
    declarations              local variable declarations
    statements
    return value;
}
/*   */                         comments
main (int argc, char *argv[])   main with arguments
exit (arg)                      terminate execution

C Preprocessor

include library file		#include <filename>
include user file		#include "filename"
replacement text		#define name text
replacement macro		#define name(var) text
       Example:    #define max(A,B) ((A)>(B) ? (A) : (B))
undefined			#undef name
quoted string in replace		#
concatenate args and rescan	##
conditional execution		#if, #else, #elif, #endif
is name defined or not?		#ifdef, #ifundef
name defined?		defined(name)
line continuation character	\

Data Types/Declarations

charater (1 byte)		char
integer			int
float (single precission)		float
float (double precission)		double
short (16 bit integer)		short
long (32 bit integer)		long
positive and negative		signed
only positive		unsigned
pointer to int, float, ..		*int, *float, ...
enumeration constant		enum

constant (unchanging) value	const
declare external variable		extern
register variable		register
local to source file		static
no value			void
structure			struct
create name by data type		typedef typename
size of an object (type is size_t)	sizeof (type)

Initialising

initialize variable	type name=value
initialize array	type name[]={value 1,... }
initialize char string	char name[]="string"

Constants

long (suffix)			L or l
float (suffix)			F or f
exponential form		e
octal (prefix zero)		0
hexadecimal (prefix)		0x or 0X
character constant (char)	'a'
char constant (oct)		'\ooo'
char constant (hex)		'\xhh'
newline, cr, tab, backspace	\n, \r, \t, \b
special characters		\\, \?, \', \"
string constants (ends with '\0')	"abc...de"

Pointers, Arrays & Structures

declare pointer to type		type *name
declare function returning pointer to type
			type *f()
declare pointer to function returning type 
			type (*pf)()
generic pointer type		void *
null pointer			NULL
object pointed to by pointer	*pointer
address of object name		&name
array			name[dim]
multi-dim array		name[dim1][dim2]...

Structures

struct tag {       structure template
               declarations
        };
create structure		struct tag name
member of structure from template	name.member
member of pointed to structure	pointer -> member
     Example. (*p).x and p->x are the same
single value, multiple type structure	 union
bit held with b bits		member : b

ANSI Standard Libraries

<assert.h> <ctype.h> <errno.h> <float.h> <limits.h>
<locale.h> <math.h> <setjmp.h> <signal.h> <stdarg.h>
<stddef.h> <stdio.h> <stdlib.h> <string.h> <time.h>

Character Class Tests <ctype.h>

alphanumeric?			isalnum(c)
alphabetic?				isalpha(c)
control character?			iscntrl(c)
decimal digit?			isdigit(c)
printing character (not incl space)?		isgraph(c)
lower case letter?			islower(c)
printing character (incl space)?		isprint(c)
printing char except space, letter, digit?	ispunct(c)
space, formfeed, newline, cr, tab, vtab?	isspace(c)
upper case letter?			isupper(c)
hexadecimal digit?			isxdigit(c)
convert to lower case?			tolower(c)
convert to upper case?			toupper(c)