C Reference Card (ANSI) Program Structure/Functions type fnc(type1,...); function prototype type name; variable declaration int main(void) { main routine declarations local variable declarations statements } type fnc(arg1,...){ function definition declarations local variable declarations statements return value; } /* */ comments int 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 # Example.#define msg(A) printf("%s = %d", #A, (A)) 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 real number (single, double precision) float, double short (16 bit integer) short long (32 bit integer) long double long (64 bit integer) long long positive or negative signed non-negative modulo 2m unsigned pointer to int, float,... int*, float*,... enumeration constant enum tag {name1=value1,...}; constant (read-only) value type const name; declare external variable extern internal to source file static local persistent between calls static no value void structure struct tag {...}; create new name for data type typedef type name; size of an object (type is size_t) sizeof object size of a data type (type is size_t) sizeof(type) Initialization initialize variable type name=value; initialize array type name[]={value1,...}; initialize char string char name[]="string"; c° 2007 Joseph H. Silverman Permissions on back. v2.2 Constants suffix: long, unsigned, float 65536L, -1U, 3.0F exponential form 4.2e1 prefix: octal, hexadecimal 0, 0x or 0X Example. 031 is 25, 0x31 is 49 decimal 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 constant 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 object, multiple possible types union bit field with b bits unsigned member: b; Operators (grouped by precedence) struct member operator name.member struct member through 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] <<, >> relational comparisons >, >=, <, <= equality comparisons ==, != and [bit op] & exclusive or [bit op] ^ or (inclusive) [bit op] | 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 delimiters {} exit from switch, while, do, for break; next iteration of while, do, for continue; go to goto label; label label: statement return value from function return expr Flow Constructions if statement if (expr1) statement1 else if (expr2) statement2 else statement3 while statement while (expr) statement for statement for (expr1; 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 is a string; cs, ct are constant strings length of s strlen(s) copy ct to s strcpy(s,ct) concatenate ct after s strcat(s,ct) 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 s memset(s,c,n) C Reference Card (ANSI) Input/Output Standard I/O standard input stream stdin standard output stream stdout standard error stream stderr end of file (type is int) 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,...) 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), b (binary) 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,...) read and store n elts to *ptr fread(*ptr,eltsize,n,fp) write n elts from *ptr to file fwrite(*ptr,eltsize,n,fp) close file fclose(fp) non-zero if error ferror(fp) non-zero if already reached 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 (printf) e,E exponential f float (scanf) lf double (scanf) 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 ap; 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); 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) returns 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 storage newptr = realloc(ptr,size); deallocate storage free(ptr); Array Functions search array for key bsearch(key,array,n,size,cmpf) sort array ascending order qsort(array,n,size,cmpf) 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 struct 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, followed by minimum re- quired values (if significantly different). CHAR_BIT bits in char (8) CHAR_MAX max value of char (SCHAR_MAX or UCHAR_MAX) CHAR_MIN min value of char (SCHAR MIN or 0) SCHAR_MAX max signed char (+127) SCHAR_MIN min signed char (−128) SHRT_MAX max value of short (+32,767) SHRT_MIN min value of short (−32,768) INT_MAX max value of int (+2,147,483,647) (+32,767) INT_MIN min value of int (−2,147,483,648) (−32,767) LONG_MAX max value of long (+2,147,483,647) LONG_MIN min value of long (−2,147,483,648) UCHAR_MAX max unsigned char (255) USHRT_MAX max unsigned short (65,535) UINT_MAX max unsigned int (4,294,967,295) (65,535) ULONG_MAX max unsigned long (4,294,967,295) Float Type Limits The numbers given in parentheses are typical values for the constants on a 32-bit Unix system. 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 1.0f + x 6= 1.0f (1.1E − 7) FLT_MANT_DIG number of digits in mantissa FLT_MAX maximum float number (3.4E38) FLT_MAX_EXP maximum exponent FLT_MIN minimum float number (1.2E − 38) FLT_MIN_EXP minimum exponent DBL_DIG decimal digits of precision (15) DBL_EPSILON smallest x so 1.0 + x 6= 1.0 (2.2E − 16) DBL_MANT_DIG number of digits in mantissa DBL_MAX max double number (1.8E308) DBL_MAX_EXP maximum exponent DBL_MIN min double number (2.2E − 308) DBL_MIN_EXP minimum exponent 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. hjhs@math.brown.edui