C Reference Card (ANSI) 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 definition declarations local variable declarations statements return value; } /* */ comments main(int argc, char *argv[]) main with args 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)) undefine #undef name quoted string in replace # concatenate args and rescan ## conditional execution #if, #else, #elif, #endif is name defined, not defined? #ifdef, #ifndef name defined? defined(name) line continuation char \ Data Types/Declarations character (1 byte) char integer int float (single precision) float float (double precision) 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 object size of a data type (type is size_t) sizeof(type name) Initialization initialize variable type name=value initialize array type name[]={value1,. . . } initialize char string char name[]="string" c 1999 Joseph H. Silverman Permissions on back. v1.3 Constants long (suffix) L or l float (suffix) F or f exponential form e octal (prefix zero) 0 hexadecimal (prefix zero-ex) 0x or 0X character constant (char, octal, hex) 'a', '\ooo', '\xhh' newline, cr, tab, backspace \n, \r, \t, \b special characters \\, \?, \', \" string constant (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 declaration of members }; 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 field with b bits member : b Operators (grouped by precedence) structure member operator name.member structure pointer pointer->member increment, decrement ++, -- plus, minus, logical not, bitwise not +, -, !, ~ indirection via pointer, address of object *pointer, &name cast expression to type (type) expr size of an object sizeof multiply, divide, modulus (remainder) *, /, % add, subtract +, - left, right shift [bit ops] <<, >> comparisons >, >=, <, <= comparisons ==, != bitwise and & bitwise exclusive or ^ bitwise or (incl) | logical and && logical or || conditional expression expr1 ? expr2 : expr3 assignment operators +=, -=, *=, . . . expression evaluation separator , Unary operators, conditional expression and assignment oper- ators group right to left; all others group left to right. 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; expr2; expr3) statement do statement do statement while(expr); switch statement switch (expr) { case const1: statement1 break; case const2: statement2 break; default: statement } ANSI Standard Libraries Character Class Tests 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) String Operations 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 first n chars strncmp(cs,ct,n) pointer to first 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 first c in first n chars of cs memchr(cs,c,n) put c into first n chars of cs memset(s,c,n) 1 2 3 C Reference Card (ANSI) Input/Output Standard I/O standard input stream stdin standard output stream stdout standard error stream stderr end of file EOF get a character getchar() print a character putchar(chr) print formatted data printf("format",arg1,. . . ) print to string s sprintf(s,"format ",arg1,. . . ) read formatted data scanf("format",&name1,. . . ) read from string s sscanf(s,"format",&name1,. . . ) read line to string s (< max chars) gets(s,max) print string s puts(s) File I/O declare file pointer FILE *fp pointer to named file fopen("name","mode") modes: r (read), w (write), a (append) get a character getc(fp) write a character putc(chr,fp) write to file fprintf(fp,"format",arg1,. . . ) read from file fscanf(fp,"format",arg1,. . . ) close file 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 field 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 Variable Argument Lists declaration of pointer to arguments va_list name; initialization of argument pointer va_start(name,lastarg) lastarg is last named parameter of the function access next unamed arg, update pointer va_arg(name,type) call before exiting function va_end(name) Standard Utility Functions 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) terminate program execution exit(status) pass string s to system for execution system(s) Conversions convert string s to double atof(s) convert string s to integer atoi(s) convert string s to long atol(s) convert prefix of s to double strtod(s,endp) convert prefix of s (base b) to long strtol(s,endp,b) same, but unsigned long strtoul(s,endp,b) Storage Allocation allocate storage malloc(size), calloc(nobj,size) change size of object realloc(pts,size) deallocate space free(ptr) Array Functions search array for key bsearch(key,array,n,size,cmp()) sort array ascending order qsort(array,n,size,cmp()) Time and Date Functions processor time used by program clock() Example. clock()/CLOCKS_PER_SEC is time in seconds current calendar time time() time2-time1 in seconds (double) difftime(time2,time1) arithmetic types representing times clock_t,time_t structure type for calendar time comps tm tm_sec seconds after minute tm_min minutes after hour tm_hour hours since midnight tm_mday day of month tm_mon months since January tm_year years since 1900 tm_wday days since Sunday tm_yday days since January 1 tm_isdst Daylight Savings Time flag convert local time to calendar time mktime(tp) convert time in tp to string asctime(tp) convert calendar time in tp to local time ctime(tp) convert calendar time to GMT gmtime(tp) convert calendar time to local time localtime(tp) format date and time info strftime(s,smax,"format ",tp) tp is a pointer to a structure of type tm Mathematical Functions Arguments and returned values are double trig functions sin(x), cos(x), tan(x) inverse trig functions asin(x), acos(x), atan(x) arctan(y/x) atan2(y,x) hyperbolic trig functions sinh(x), cosh(x), tanh(x) exponentials & logs exp(x), log(x), log10(x) exponentials & logs (2 power) ldexp(x,n), frexp(x,*e) division & remainder modf(x,*ip), fmod(x,y) powers pow(x,y), sqrt(x) rounding ceil(x), floor(x), fabs(x) Integer Type Limits 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 FLT_RADIX radix of exponent rep (2) FLT_ROUNDS floating point rounding mode FLT_DIG decimal digits of precision (6) FLT_EPSILON smallest x so 1.0 + x 6= 1.0 (10− 5) FLT_MANT_DIG number of digits in mantissa FLT_MAX maximum floating point number (1037) FLT_MAX_EXP maximum exponent FLT_MIN minimum floating point number (10− 37) FLT_MIN_EXP minimum exponent DBL_DIG decimal digits of precision (10) DBL_EPSILON smallest x so 1.0 + x 6= 1.0 (10− 9) DBL_MANT_DIG number of digits in mantissa DBL_MAX max double floating point number (1037) DBL_MAX_EXP maximum exponent DBL_MIN min double floating point number (10− 37) DBL_MIN_EXP minimum exponent May 1999 v1.3. Copyright c 1999 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. hjhs@math.brown.edui 4 5 6
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