Reference C Card (ANSI)
Program Structure/Functions
type fnc(type 1 ,. . . ) type name main() { declarations statements } type fnc(arg 1 ,. . . ) { declarations statements return value; } /* */ main(int argc, char *argv[]) exit(arg ) function declarations external variable declarations main routine local variable declarations function denition local variable declarations
Constants
long (sux) oat (sux) exponential form octal (prex zero) hexadecimal (prex zero-ex) character constant (char, octal, hex) newline, cr, tab, backspace special characters string constant (ends with '\0') L or l F or f e 0 0x or 0X 'a', '\ooo', '\xhh' \n, \r, \t, \b \\, \?, \', \" "abc. . . de"
Flow of Control
statement terminator ; block delimeters {} exit from switch, while, do, for break next iteration of while, do, for continue go to goto label label label : return value from function return expr Flow Constructions if statement if (expr ) statement else if (expr ) statement else statement while statement while (expr ) statement for statement for (expr 1 ; expr 2 ; expr 3 ) statement do statement do statement while(expr ); switch statement switch (expr ) { case const 1 : statement 1 break; case const 2 : statement 2 break; default: statement }
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 null pointer object pointed to by pointer *pointer address of object name &name array name[dim ] name[dim 1 ][dim 2 ]. . . multi-dim array Structures struct tag { structure template declarations declaration of members }; struct tag name create structure 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 eld with b bits member : b
comments main with args terminate execution
C Preprocessor
include library le #include <lename> include user le #include "lename" replacement text #define name text replacement macro #define name(var ) text Example. #define max(A,B) ((A)>(B) ? (A) : (B)) undene #undef name quoted string in replace # concatenate args and rescan ## conditional execution #if, #else, #elif, #endif is name dened, not dened? #ifdef, #ifndef name dened? defined(name ) line continuation char \
ANSI Standard Libraries
<assert.h> <locale.h> <stddef.h> <ctype.h> <math.h> <stdio.h> <errno.h> <setjmp.h> <stdlib.h> <float.h> <signal.h> <string.h> <limits.h> <stdarg.h> <time.h>
Character Class Tests <ctype.h>
alphanumeric? alphabetic? control character? decimal digit? printing character (not incl space)? lower case letter? printing character (incl space)? printing char except space, letter, digit? space, formfeed, newline, cr, tab, vtab? upper case letter? hexadecimal digit? convert to lower case? convert to upper case? isalnum(c) isalpha(c) iscntrl(c) isdigit(c) isgraph(c) islower(c) isprint(c) ispunct(c) isspace(c) isupper(c) isxdigit(c) tolower(c) toupper(c)
Data Types/Declarations
character (1 byte) integer oat (single precision) oat (double precision) short (16 bit integer) long (32 bit integer) positive and negative only positive pointer to int, float,. . . enumeration constant constant (unchanging) value declare external variable register variable local to source le no value structure create name by data type size of an object (type is size_t) size of a data type (type is size_t) char int float double short long signed unsigned *int, *float,. . . enum const extern register static void struct typedef typename sizeof object sizeof(type name)
Operators (grouped by precedence)
structure member operator structure pointer increment, decrement plus, minus, logical not, bitwise not indirection via pointer, address of object cast expression to type size of an object multiply, divide, modulus (remainder) add, subtract left, right shift [bit ops] comparisons comparisons bitwise and bitwise exclusive or bitwise or (incl) name.member pointer ->member ++, -+, -, !, ~ *pointer , &name (type) expr sizeof *, /, % +, <<, >> >, >=, <, <= ==, != & ^ |
String Operations <string.h>
s,t are strings, cs,ct are constant strings length of s strlen(s) copy ct to s strcpy(s,ct) up to n chars strncpy(s,ct,n) concatenate ct after s strcat(s,ct) up to n chars strncat(s,ct,n) compare cs to ct strcmp(cs,ct) only rst n chars strncmp(cs,ct,n) pointer to rst c in cs strchr(cs,c) pointer to last c in cs strrchr(cs,c) copy n chars from ct to s memcpy(s,ct,n) copy n chars from ct to s (may overlap) memmove(s,ct,n) compare n chars of cs with ct memcmp(cs,ct,n) pointer to rst c in rst n chars of cs memchr(cs,c,n) put c into rst n chars of cs memset(s,c,n)
Initialization
initialize variable initialize array initialize char string type name=value type name[]={value 1 ,. . . } char name[]="string "
logical and && logical or || conditional expression expr 1 ? expr 2 : expr 3 assignment operators +=, -=, *=, . . . expression evaluation separator , Unary operators, conditional expression and assignment operators group right to left; all others group left to right. 2
c 1999 Joseph H. Silverman Permissions on back. v1.3
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C Reference Card (ANSI)
Input/Output <stdio.h>
Standard I/O standard input stream stdin standard output stream stdout standard error stream stderr end of le EOF get a character getchar() a print character putchar(chr ) print formatted data printf("format ",arg 1 ,. . . ) print to string s sprintf(s,"format ",arg 1 ,. . . ) read formatted data scanf("format ",&name 1 ,. . . ) read from string s sscanf(s,"format ",&name 1 ,. . . ) read line to string s (< max chars) gets(s,max) print string s puts(s) File I/O declare le pointer FILE *fp pointer to named le fopen("name ","mode ") modes: r (read), w (write), a (append) get a character getc(fp) write a character putc(chr ,fp) write to le fprintf(fp,"format ",arg 1 ,. . . ) read from le fscanf(fp,"format ",arg 1 ,. . . ) close le fclose(fp) non-zero if error ferror(fp) non-zero if EOF feof(fp) read line to string s (< max chars) fgets(s,max,fp ) write string s fputs(s,fp ) Codes for Formatted I/O: "%-+ 0w.pmc" - left justify + print with sign space print space if no sign 0 pad with leading zeros w min eld width p precision m conversion character: h short, l long, L long double c conversion character: d,i integer u unsigned c single char s char string f double e,E exponential o octal x,X hexadecimal p pointer n number of chars written g,G same as f or e,E depending on exponent
Standard Utility Functions <stdlib.h>
absolute value of int n abs(n) absolute value of long n labs(n) quotient and remainder of ints n,d div(n,d) retursn structure with div_t.quot and div_t.rem quotient and remainder of longs n,d ldiv(n,d) returns structure with ldiv_t.quot and ldiv_t.rem pseudo-random integer [0,RAND_MAX] rand() set random seed to n srand(n) exit(status) terminate program execution pass string s to system for execution system(s) Conversions convert string s to double atof(s) atoi(s) convert string s to integer convert string s to long atol(s) convert prex of s to double strtod(s,endp) strtol(s,endp,b) convert prex of s (base b) to long same, but unsigned long strtoul(s,endp,b) Storage Allocation allocate storage malloc(size), calloc(nobj,size) realloc(pts,size) change size of object deallocate space free(ptr) Array Functions bsearch(key,array,n,size,cmp()) search array for key sort array ascending order qsort(array,n,size,cmp())
Integer Type Limits <limits.h>
The numbers given in parentheses are typical values for the constants on a 32-bit Unix system. CHAR_BIT bits in char (8) CHAR_MAX max value of char (127 or 255) CHAR_MIN min value of char (128 or 0) INT_MAX max value of int (+32,767) INT_MIN min value of int (32,768) LONG_MAX max value of long (+2,147,483,647) LONG_MIN min value of long (2,147,483,648) SCHAR_MAX max value of signed char (+127) SCHAR_MIN min value of signed char (128) SHRT_MAX max value of short (+32,767) SHRT_MIN min value of short (32,768) UCHAR_MAX max value of unsigned char (255) UINT_MAX max value of unsigned int (65,535) ULONG_MAX max value of unsigned long (4,294,967,295) USHRT_MAX max value of unsigned short (65,536)
Float Type Limits <float.h>
FLT_RADIX FLT_ROUNDS FLT_DIG FLT_EPSILON FLT_MANT_DIG FLT_MAX FLT_MAX_EXP FLT_MIN FLT_MIN_EXP DBL_DIG DBL_EPSILON DBL_MANT_DIG DBL_MAX DBL_MAX_EXP DBL_MIN DBL_MIN_EXP radix of exponent rep oating point rounding mode decimal digits of precision smallest x so 1.0 + x = 1.0 number of digits in mantissa maximum oating point number maximum exponent minimum oating point...