Guia de referência rápida sobre C.

1. C Reference Card (ANSI) Constants Flow of Control
suffix: long, unsigned, float 65536L, -1U, 3.0F statement terminator ;
Program Structure/Functions exponential form 4.2e1 block delimiters {}
prefix: octal, hexadecimal 0, 0x or 0X exit from switch, while, do, for break;
type fnc(type 1 , . . . ); function prototype
Example. 031 is 25, 0x31 is 49 decimal next iteration of while, do, for continue;
type name; variable declaration
character constant (char, octal, hex) 'a', 'ooo', 'xhh' go to goto label;
int main(void) { main routine
local variable declarations newline, cr, tab, backspace n, r, t, b label label: statement
declarations
special characters , ?, ', quot; return value from function return expr
statements
string constant (ends with '0') quot;abc. . . dequot; Flow Constructions
}
if statement if (expr 1 ) statement 1
type fnc(arg 1 , . . . ) { function definition
local variable declarations Pointers, Arrays & Structures else if (expr 2 ) statement 2
declarations
else statement 3
statements declare pointer to type type *name;
while statement while (expr )
return value; declare function returning pointer to type type *f();
statement
} declare pointer to function returning type type (*pf)();
for statement for (expr 1 ; expr 2 ; expr 3 )
/* */ comments generic pointer type void *
statement
int main(int argc, char *argv[]) main with args null pointer constant NULL
do statement do statement
exit(arg); terminate execution object pointed to by pointer *pointer
while(expr );
address of object name &name
C Preprocessor switch statement switch (expr ) {
array name[dim]
case const 1 : statement 1 break;
include library file #include <filename> multi-dim array name[dim 1 ][dim 2 ]. . . case const 2 : statement 2 break;
include user file #include quot;filenamequot; Structures default: statement
replacement text #define name text struct tag { structure template }
replacement macro #define name(var ) text declarations declaration of members
ANSI Standard Libraries
Example. #define max(A,B) ((A)>(B) ? (A) : (B)) };
undefine #undef name <assert.h> <ctype.h> <errno.h> <float.h> <limits.h>
create structure struct tag name
quoted string in replace # <locale.h> <math.h> <setjmp.h> <signal.h> <stdarg.h>
member of structure from template name.member
Example. #define msg(A) printf(quot;%s = %dquot;, #A, (A)) <stddef.h> <stdio.h> <stdlib.h> <string.h> <time.h>
member of pointed-to structure pointer -> member
concatenate args and rescan ## Example. (*p).x and p->x are the same
Character Class Tests <ctype.h>
conditional execution #if, #else, #elif, #endif single object, multiple possible types union
is name defined, not defined? #ifdef, #ifndef alphanumeric? isalnum(c)
bit field with b bits unsigned member : b;
name defined? defined(name) alphabetic? isalpha(c)
Operators (grouped by precedence)
line continuation char control character? iscntrl(c)
decimal digit? isdigit(c)
Data Types/Declarations struct member operator name.member
printing character (not incl space)? isgraph(c)
struct member through pointer pointer ->member
character (1 byte) char lower case letter? islower(c)
increment, decrement ++, --
integer int printing character (incl space)? isprint(c)
plus, minus, logical not, bitwise not +, -, !, ~
real number (single, double precision) float, double printing char except space, letter, digit? ispunct(c)
indirection via pointer, address of object *pointer , &name
short (16 bit integer) short space, formfeed, newline, cr, tab, vtab? isspace(c)
cast expression to type (type) expr
long (32 bit integer) long upper case letter? isupper(c)
size of an object sizeof
double long (64 bit integer) long long hexadecimal digit? isxdigit(c)
positive or negative signed multiply, divide, modulus (remainder) *, /, % convert to lower case tolower(c)
non-negative modulo 2m unsigned convert to upper case toupper(c)
add, subtract +, -
pointer to int, float,. . . int*, float*,. . .
String Operations <string.h>
left, right shift [bit ops] <<, >>
enumeration constant enum tag {name 1 =value 1 ,. . . };
relational comparisons >, >=, <, <= s is a string; cs, ct are constant strings
constant (read-only) value type const name;
declare external variable extern equality comparisons ==, != length of s strlen(s)
internal to source file static copy ct to s strcpy(s,ct)
and [bit op] &
local persistent between calls static concatenate ct after s strcat(s,ct)
exclusive or [bit op] ^
no value void compare cs to ct strcmp(cs,ct)
or (inclusive) [bit op] |
structure struct tag {. . . }; only first n chars strncmp(cs,ct,n)
create new name for data type typedef type name; logical and && pointer to first c in cs strchr(cs,c)
size of an object (type is size_t) sizeof object pointer to last c in cs strrchr(cs,c)
logical or ||
size of a data type (type is size_t) sizeof(type) copy n chars from ct to s memcpy(s,ct,n)
conditional expression expr 1 ? expr 2 : expr 3
copy n chars from ct to s (may overlap) memmove(s,ct,n)
Initialization assignment operators +=, -=, *=, . . . compare n chars of cs with ct memcmp(cs,ct,n)
initialize variable type name=value; expression evaluation separator , pointer to first c in first n chars of cs memchr(cs,c,n)
initialize array type name[]={value 1 ,. . . }; put c into first n chars of s memset(s,c,n)
Unary operators, conditional expression and assignment oper-
initialize char string char name[]=quot;stringquot;; ators group right to left; all others group left to right.
c 2007 Joseph H. Silverman Permissions on back. v2.2

2. C Reference Card (ANSI) Standard Utility Functions <stdlib.h> Mathematical Functions <math.h>
Arguments and returned values are double
absolute value of int n abs(n)
Input/Output <stdio.h> absolute value of long n labs(n) trig functions sin(x), cos(x), tan(x)
quotient and remainder of ints n,d div(n,d) inverse trig functions asin(x), acos(x), atan(x)
Standard I/O
returns structure with div_t.quot and div_t.rem arctan(y/x) atan2(y,x)
standard input stream stdin
quotient and remainder of longs n,d ldiv(n,d) hyperbolic trig functions sinh(x), cosh(x), tanh(x)
standard output stream stdout
returns structure with ldiv_t.quot and ldiv_t.rem exponentials & logs exp(x), log(x), log10(x)
standard error stream stderr
pseudo-random integer [0,RAND_MAX] rand() exponentials & logs (2 power) ldexp(x,n), frexp(x,&e)
end of file (type is int) EOF
set random seed to n srand(n) division & remainder modf(x,ip), fmod(x,y)
get a character getchar()
terminate program execution exit(status) powers pow(x,y), sqrt(x)
print a character putchar(chr )
pass string s to system for execution system(s) rounding ceil(x), floor(x), fabs(x)
print formatted data printf(quot;formatquot;,arg 1 ,. . . )
Conversions
Integer Type Limits <limits.h>
print to string s sprintf(s,quot;formatquot;,arg 1 ,. . . )
convert string s to double atof(s)
read formatted data scanf(quot;formatquot;,&name 1 ,. . . )
convert string s to integer atoi(s) The numbers given in parentheses are typical values for the
read from string s sscanf(s,quot;formatquot;,&name 1 ,. . . )
convert string s to long atol(s) constants on a 32-bit Unix system, followed by minimum re-
print string s puts(s)
convert prefix of s to double strtod(s,&endp) quired values (if significantly different).
File I/O
convert prefix of s (base b) to long strtol(s,&endp,b) CHAR_BIT bits in char (8)
declare file pointer FILE *fp;
same, but unsigned long strtoul(s,&endp,b) CHAR_MAX max value of char (SCHAR_MAX or UCHAR_MAX)
pointer to named file fopen(quot;namequot;,quot;modequot;)
Storage Allocation CHAR_MIN min value of char (SCHAR MIN or 0)
modes: r (read), w (write), a (append), b (binary)
allocate storage malloc(size), calloc(nobj,size) SCHAR_MAX max signed char (+127)
get a character getc(fp)
change size of storage newptr = realloc(ptr,size); SCHAR_MIN min signed char (−128)
write a character putc(chr ,fp)
deallocate storage free(ptr); SHRT_MAX max value of short (+32,767)
write to file fprintf(fp,quot;formatquot;,arg 1 ,. . . )
Array Functions SHRT_MIN min value of short (−32,768)
read from file fscanf(fp,quot;formatquot;,arg 1 ,. . . )
search array for key bsearch(key,array,n,size,cmpf) INT_MAX max value of int (+2,147,483,647) (+32,767)
read and store n elts to *ptr fread(*ptr,eltsize,n,fp)
sort array ascending order qsort(array,n,size,cmpf) INT_MIN min value of int (−2,147,483,648) (−32,767)
write n elts from *ptr to file fwrite(*ptr,eltsize,n,fp)
LONG_MAX max value of long (+2,147,483,647)
Time and Date Functions <time.h>
close file fclose(fp)
LONG_MIN min value of long (−2,147,483,648)
non-zero if error ferror(fp)
UCHAR_MAX max unsigned char (255)
processor time used by program clock()
non-zero if already reached EOF feof(fp)
USHRT_MAX max unsigned short (65,535)
Example. clock()/CLOCKS_PER_SEC is time in seconds
read line to string s (< max chars) fgets(s,max,fp)
UINT_MAX max unsigned int (4,294,967,295) (65,535)
current calendar time time()
write string s fputs(s,fp)
ULONG_MAX max unsigned long (4,294,967,295)
time2 -time1 in seconds (double) difftime(time2 ,time1 )
Codes for Formatted I/O: quot;%-+ 0w.pmcquot;
arithmetic types representing times clock_t,time_t
Float Type Limits <float.h>
- left justify
structure type for calendar time comps struct tm
+ print with sign
tm_sec seconds after minute The numbers given in parentheses are typical values for the
space print space if no sign
tm_min minutes after hour constants on a 32-bit Unix system.
0 pad with leading zeros
tm_hour hours since midnight FLT_RADIX radix of exponent rep (2)
w min field width
tm_mday day of month FLT_ROUNDS floating point rounding mode
p precision
tm_mon months since January FLT_DIG decimal digits of precision (6)
m conversion character:
tm_year years since 1900 FLT_EPSILON smallest x so 1.0f + x = 1.0f (1.1E − 7)
h short, l long, L long double
tm_wday days since Sunday FLT_MANT_DIG number of digits in mantissa
c conversion character:
tm_yday days since January 1 FLT_MAX maximum float number (3.4E38)
d,i integer u unsigned
tm_isdst Daylight Savings Time flag FLT_MAX_EXP maximum exponent
c single char s char string
FLT_MIN minimum float number (1.2E − 38)
f double (printf) e,E exponential convert local time to calendar time mktime(tp)
FLT_MIN_EXP minimum exponent
f float (scanf) lf double (scanf) convert time in tp to string asctime(tp)
DBL_DIG decimal digits of precision (15)
o octal x,X hexadecimal convert calendar time in tp to local time ctime(tp)
DBL_EPSILON smallest x so 1.0 + x = 1.0 (2.2E − 16)
p pointer n number of chars written convert calendar time to GMT gmtime(tp)
DBL_MANT_DIG number of digits in mantissa
g,G same as f or e,E depending on exponent convert calendar time to local time localtime(tp)
DBL_MAX max double number (1.8E308)
format date and time info strftime(s,smax,quot;formatquot;,tp)
Variable Argument Lists <stdarg.h> DBL_MAX_EXP maximum exponent
tp is a pointer to a structure of type tm
DBL_MIN min double number (2.2E − 308)
declaration of pointer to arguments va_list ap;
DBL_MIN_EXP minimum exponent
initialization of argument pointer va_start(ap,lastarg);
lastarg is last named parameter of the function
access next unnamed arg, update pointer va_arg(ap,type)
call before exiting function va_end(ap); January 2007 v2.2. Copyright c 2007 Joseph H. Silverman
Permission is granted to make and distribute copies of this card pro-
vided the copyright notice and this permission notice are preserved on
all copies.
Send comments and corrections to J.H. Silverman, Math. Dept., Brown
Univ., Providence, RI 02912 USA. jhs@math.brown.edu