| # and ## | manipulate strings | 
	
		| #define | define variables | 
	
		| #error | display an error message | 
	
		| #if, #ifdef, #ifndef, #else, #elif, #endif | conditional operators | 
	
		| #include | insert the contents of another file | 
	
		| #line | set line and file information | 
	
		| #pragma | implementation specific command | 
	
		| #undef | used to undefine variables | 
	
		| Predefined preprocessor variables | miscellaneous preprocessor variables | 
	
		| abort | stops the program | 
	
		| abs | absolute value | 
	
		| acos | arc cosine | 
	
		| asctime | a textual version of the time | 
	
		| asin | arc sine | 
	
		| assert | stops the program if an expression isn't true | 
	
		| atan | arc tangent | 
	
		| atan2 | arc tangent, using signs to determine quadrants | 
	
		| atexit | sets a function to be called when the program exits | 
	
		| atof | converts a string to a double | 
	
		| atoi | converts a string to an integer | 
	
		| atol | converts a string to a long | 
	
		| bsearch | perform a binary search | 
	
		| calloc | allocates and clears a two-dimensional chunk of memory | 
	
		| ceil | the smallest integer not less than a certain value | 
	
		| clearerr | clears errors | 
	
		| clock | returns the amount of time that the program has been running | 
	
		| cos | cosine | 
	
		| cosh | hyperbolic cosine | 
	
		| ctime | returns a specifically formatted version of the time | 
	
		| difftime | the difference between two times | 
	
		| div | returns the quotient and remainder of a division | 
	
		| exit | stop the program | 
	
		| exp | returns āeā raised to a given power | 
	
		| fabs | absolute value for floating-point numbers | 
	
		| fclose | close a file | 
	
		| feof | true if at the end-of-file | 
	
		| ferror | checks for a file error | 
	
		| fflush | writes the contents of the output buffer | 
	
		| fgetc | get a character from a stream | 
	
		| fgetpos | get the file position indicator | 
	
		| fgets | get a string of characters from a stream | 
	
		| floor | returns the largest integer not greater than a given value | 
	
		| fmod | returns the remainder of a division | 
	
		| fopen | open a file | 
	
		| fprintf | print formatted output to a file | 
	
		| fputc | write a character to a file | 
	
		| fputs | write a string to a file | 
	
		| fread | read from a file | 
	
		| free | returns previously allocated memory to the operating system | 
	
		| freopen | open an existing stream with a different name | 
	
		| frexp | decomposes a number into scientific notation | 
	
		| fscanf | read formatted input from a file | 
	
		| fseek | move to a specific location in a file | 
	
		| fsetpos | move to a specific location in a file | 
	
		| ftell | returns the current file position indicator | 
	
		| fwrite | write to a file | 
	
		| getc | read a character from a file | 
	
		| getchar | read a character from STDIN | 
	
		| getenv | get enviornment information about a variable | 
	
		| gets | read a string from STDIN | 
	
		| gmtime | returns a pointer to the current Greenwich Mean Time | 
	
		| isalnum | true if a character is alphanumeric | 
	
		| isalpha | true if a character is alphabetic | 
	
		| iscntrl | true if a character is a control character | 
	
		| isdigit | true if a character is a digit | 
	
		| isgraph | true if a character is a graphical character | 
	
		| islower | true if a character is lowercase | 
	
		| isprint | true if a character is a printing character | 
	
		| ispunct | true if a character is punctuation | 
	
		| isspace | true if a character is a space character | 
	
		| isupper | true if a character is an uppercase character | 
	
		| isxdigit | true if a character is a hexidecimal character | 
	
		| labs | absolute value for long integers | 
	
		| ldexp | computes a number in scientific notation | 
	
		| ldiv | returns the quotient and remainder of a division, in long integer form | 
	
		| localtime | returns a pointer to the current time | 
	
		| log | natural logarithm | 
	
		| log10 | natural logarithm, in base 10 | 
	
		| longjmp | start execution at a certain point in the program | 
	
		| malloc | allocates memory | 
	
		| memchr | searches an array for the first occurance of a character | 
	
		| memcmp | compares two buffers | 
	
		| memcpy | copies one buffer to another | 
	
		| memmove | moves one buffer to another | 
	
		| memset | fills a buffer with a character | 
	
		| mktime | returns the calendar version of a given time | 
	
		| modf | decomposes a number into integer and fractional parts | 
	
		| perror | displays a string version of the current error to STDERR | 
	
		| pow | returns a given number raised to another number | 
	
		| printf | write formatted output to STDOUT | 
	
		| putc | write a character to a stream | 
	
		| putchar | write a character to STDOUT | 
	
		| putenv | add/modify the environmental settings | 
	
		| puts | write a string to STDOUT | 
	
		| qsort | perform a quicksort | 
	
		| raise | send a signal to the program | 
	
		| rand | returns a pseudorandom number | 
	
		| realloc | changes the size of previously allocated memory | 
	
		| remove | erase a file | 
	
		| rename | rename a file | 
	
		| rewind | move the file position indicator to the beginning of a file | 
	
		| scanf | read formatted input from STDIN | 
	
		| setbuf | set the buffer for a specific stream | 
	
		| setjmp | set execution to start at a certain point | 
	
		| setlocale | sets the current locale | 
	
		| setvbuf | set the buffer and size for a specific stream | 
	
		| signal | register a function as a signal handler | 
	
		| sin | sine | 
	
		| sinh | hyperbolic sine | 
	
		| sprintf | write formatted output to a buffer | 
	
		| sqrt | square root | 
	
		| srand | initialize the random number generator | 
	
		| sscanf | read formatted input from a buffer | 
	
		| strcat | concatenates two strings | 
	
		| strchr | finds the first occurance of a character in a string | 
	
		| strcmp | compares two strings | 
	
		| strcoll | compares two strings in accordance to the current locale | 
	
		| strcpy | copies one string to another | 
	
		| strcspn | searches one string for any characters in another | 
	
		| strerror | returns a text version of a given error code | 
	
		| strftime | returns individual elements of the date and time | 
	
		| strlen | returns the length of a given string | 
	
		| strncat | concatenates a certain amount of characters of two strings | 
	
		| strncmp | compares a certain amount of characters of two strings | 
	
		| strncpy | copies a certain amount of characters from one string to another | 
	
		| strpbrk | finds the first location of any character in one string, in another string | 
	
		| strrchr | finds the last occurance of a character in a string | 
	
		| strspn | returns the length of a substring of characters of a string | 
	
		| strstr | finds the first occurance of a substring of characters | 
	
		| strtod | converts a string to a double | 
	
		| strtok | finds the next token in a string | 
	
		| strtol | converts a string to a long | 
	
		| strtoul | converts a string to an unsigned long | 
	
		| strxfrm | converts a substring so that it can be used by string comparison functions | 
	
		| system | perform a system call | 
	
		| tan | tangent | 
	
		| tanh | hyperbolic tangent | 
	
		| time | returns the current calendar time of the system | 
	
		| tmpfile | return a pointer to a temporary file | 
	
		| tmpnam | return a unique filename | 
	
		| tolower | converts a character to lowercase | 
	
		| toupper | converts a character to uppercase | 
	
		| ungetc | puts a character back into a stream | 
	
		| va_arg | use variable length parameter lists | 
	
		| vprintf, vfprintf, and vsprintf | write formatted output with variable argument lists | 
	
		| vscanf, vfscanf and vsscanf | gets formatted input from stdin with variable argument lists |