C Quick Reference

(Last Mod: 27 November 2010 21:38:36 )

Precedence of C Operators
Format codes for the printf() function family
Format codes for the scanf() function family
Abbreviated reference of commonly used functions

Precedence of C Operators

LEVEL	Description	Operator	Associativity
1	Function Expression	`( )`	left
	Array Expression	`[ ]`
	struct indirection	`->`
	struct member	`.`
2	Increment / Decrement	`++ --`	right
	Bitwise invert (1's complement)	`~`
	Logical NOT (unary NOT)	`!`
	Address	`&`
	Dereference	`*`
	Cast	`( type )`
	Unary plus (positive sign)	`+`
	Unary minus (negative sign)	`-`
	Size in bytes	`sizeof`
3	Multiplication	`*`	left
	Division	`/`
	Modulus	`%`
4	Addition	`+`
4	Subtraction	`-`
5	Shift Left	`<<`
5	Shift Right	`>>`
6	Less than	`<`
	Less than or equal	`<=`
	Greater than	`>`
	Greater than or equal	`>=`
7	Equal	`==`
7	Not equal	`!=`
8	Bitwise AND	`&`
9	Bitwise XOR	`^`
10	Bitwise OR	`\|`
11	Logical AND	`&&`
12	Logical OR	`\|\|`
13	Conditional	`? :`	right
14	Assignment	= *= /= %= += -= >>= <<= &= \|= ^=	right
15	Comma	`,`	left

Format codes for printf() function family

Format Specifier: %[flags][width][.precision][modifier][type]

Required type and optional modifiers

Modifier	Type	Format	Corresponding argument must be
INTEGER TYPES
	c	character	char, short, or int (automatically promoted to int)
	s	string	address of char (first character of null-terminated string)
	d, i	decimal	char, short, or int (automatically promoted by to int)
	o	octal
	x	hex (a..f)
	X	hex (A..F)
l	d, i	decimal	long
	o	octal
	x	hex (a..f)
	X	hex (A..F)
	u	decimal	unsigned char, unsigned short, unsigned int (automatically promoted to unsigned int)
l	u	decimal	unsigned long
FLOATING POINT TYPES
	f	m.nnnnnn	float or double (automatically promoted to double) g and G use which ever format is shortest
	e	m.nnnnnne?xx
	E	m.nnnnnnE?xx
	g	d, e, or f
	G	d, E, or f
L	f	m.nnnnnn	long double g and G use which ever format is shortest
	e	m.nnnnnne?xx
	E	m.nnnnnnE?xx
	g	d, Le, or Lf
	G	d, LE, or Lf
POINTER TYPES
	p	address	pointer (i.e., an address)
REPORT BACK
	n	characters written so far	address of variable of type int
h	n		address of variable of type short
l	n		address of variable of type long
SPECIAL CHARACTER
	%	%	no argument required/allowed

Optional Flags

Flag	Meaning
-	Left justify the result
+	Begin number with appropriate sign (+ or -)
space	Add space in place of an unused sign
#	type {o} : begin number with 0 (zero) to indicate octal
	type {x} : begin number with 0x to indicate hex
	type {X} : begin number with 0X to indicate hex
	type {e, E, f}: use a decimal point
	type {g, G}: use a decimal point and do not remove trailing zeros.
0 (zero)	Pad the number to the left with zeros

Format codes for scanf() function family

Conversion Code format: %[flags][width][modifier][type]

Required type and optional modifiers

Modifier	Type	Interpretation	Corresponding argument must be
INTEGER TYPES
	c	character	address of char
	s	string	address of char
h	d	decimal integer	address of short
			address of int
l			address of long
h	o	octal integer	address of short
			address of int
l			address of long
h	x or X	hexadecimal integer	address of short
			address of int
l			address of long
h	i	nnn - decimal integer 0nnn - octal integer 0xnnn - hex integer	address of short
			address of int
l			address of long
h	u	unsigned decimal integer	address of short
			address of int
l			address of long
FLOATING POINT TYPES
	f e, E g, G	floating point value - decimal or exponential format acceptable	address of float
l			address of double
L			address of long double
POINTER TYPES
	p	address	address of a pointer
REPORT BACK
	n	characters read so far	address of variable of type int
h			address of variable of type short
l			address of variable of type long
SPECIAL CHARACTER
	%	match the % in the input	no argument required/allowed
MATCHING/EXCLUSION
	[chars]	string that only has chars	address of char
	[^chars]	string that excludes chars	address of char

Optional Flags

Flag	Meaning
*	Suppress storage of scanned result (hence no corresponding address in list)

Width

Positive integer which specifies the maximum width of the input field. Actual width may be smaller.

Characters not in a conversion code:

whitespace - causes any whitespace to be ignored up to the next non-whitespace character.
non-whitespace - requires an exact match to next character in input stream, which is then skipped.

Abbreviated reference of commonly used functions

prototype	Comments
<stdio.h>
int printf(const char *fs [, arg, ...] );	fs = format string
int fprintf(FILE fp,const char fs [, arg, ...] );
int sprintf(char dest, const char fs [, arg, ...] );
int scanf(const char *fs [, arg, ...] );	fs = format string
int fscanf(FILE fp,const char fs [, arg, ...] );
int sscanf(const char src, const char fs [, arg, ...] );
FILE fopen(const char fn, const char *mode);	fn = filename, mode ex: "wt" "rb"
int fclose(FILE *fp);	returns 0 on success, EOF otherwise
<stdlib.h>
int rand(void);	random integer [0 ,,, RAND_MAX]
void srand(unsigned int);	seed the random number generator
double sin(double radians);	argument in radians
double cos(double radians);
double tan(double radians);
double arcsin(double x);	return value in radians
double arccos(double x);
double arctan(double x);
double atan2(double y, double x);
double exp(double x);	returns e^x
double log(double x);	returns natural logarithm of x
double log10(double radians);	returns base ten logarithm of x
double fabs(double x);	absolute value of a floating point value
<math.h>
double sin(double radians);	argument in radians
double cos(double radians);
double tan(double radians);
double arcsin(double x);	returns -(PI/2) < radians < +(PI/2)
double arccos(double x);
double arctan(double x);
double atan2(double y, double x);	returns -PI < radians < +PI
double exp(double x);	returns e^x
double log(double x);	returns natural logarithm of x
double log10(double radians);	returns base ten logarithm of x
double pow(double x, double y);	returns x to the power of y
double fabs(double x);	absolute value of a floating point value
double ceil(double x);	smallest integer not less than x
double floor(double x);	largest integer not larger than x

In-Class Developed Output Functions (using only putc())

<stdio.h>
- int putc(int c, FILE *stream);
<stdlib.h>
- EXIT_SUCCESS, EXIT_FAILURE
- size_t (integer data type suitable for representing sizes of objects in bytes)
<limits.h>
- CHAR_BIT
- INT_MIN, INT_MAX, UINT_MIN, UINT_MAX
- LONG_MIN, LONG_MAX, ULONG_MIN, ULONG_MAX
<float.h>
- FLT_MAX, DBL_MAX

To print a character to the screen:

#define PutC(c) (putc((char) (c), stdout))

To print a string to the screen:

int PutS(const char *s)

{

   int i;

   for (i = 0; '\0' != s[i]; i++ )

        PutC(s[i]);

   return i;

}

To print a single decimal digit to the screen:

#define PutD(d) (PutC('0' + (d)))

To print an unsigned integer to the screen:

int PutV_u(unsigned int n)

{

   unsigned int m;

   int printed;

   printed = 0;

   for (m = 1; n/m >= 10; m *= 10 )

        /* EMPTY LOOP */ ;

   do

   {

        for (d = 0; n >= m; d++)

            n -= m;

        PutD(d);

        printed++;

        m /= 10;

   } while (m > 0);



   return printed;

}

To print a signed integer to the screen:

int PutV_i(int n)

{

   if (n < 0)

   {

        PutC('-');

        return 1 + PutV_u(-n);

   }

   return PutV_u(n);

}

To print a floating-point value to the screen (to six decimal digits):

int PutV_lf(double x)

{

    double weight;

    int printed;

    printed = 0;

    if (x < 0)

    {

        PutC('-');

        printed++;

    }

    for (weight = 1; x/weight >= 10.0; weight *= 10 )

        /* EMPTY LOOP */ ;

    do

    {

        for (d = 0; x >= weight; d++)

            x -= weight;

        PutD(d);

        printed++;

        weight /= 10.0;

    } while (weight > 0.5);

    PutC('.');

    printed++;



        do

    {

        for (d = 0; x >= weight; d++)

            x -= weight;

        PutD(d);

        printed++;

        weight /= 10.0;

    } while (weight > 0.5e-6);



    return printed;

}