Computer & Information Sciences
University of Delaware

C++ Header Files and Standard Functions

(This info is taken from Appendix C of the nice book Data Abstraction and Problem Solving with C++, 3rd ed., by F. M. Carrano & J.J. Prichard.)

Here is a list of commonly used C++ headers. If an older version of the header exists, its name is shown in parentheses.

cassert (assert.h)

This library contains only the function assert. You use
assert(assertion);
to test the validity of an assertion. If assertion is false, assert writes an error message and terminates program execution. You can disable all occurrences of assert in your program by placing the directive
#define NDEBUG
before the include directive.

cctype (ctype.h)

Most functions in this library classify a given ASCII character as a letter, a digit, and so on. Two other functions convert letters between uppercase and lowercase.

The classification functions return a true value if ch belongs to the specified group; otherwise they return false.
isalnum(ch) Returns true if ch is either a letter or a decimal digit
isalpha(ch) Returns true if ch is a letter
iscntrl(ch) Returns true if ch is a control character (ASCII 127 or 0 to 31)
isdigit(ch) Returns true if ch is a decimal digit
isgraph(ch) Returns true if ch is printable and nonblank
islower(ch) Returns true if ch is a lowercase letter
isprint(ch) Returns true if ch is printable (including blank)
ispunct(ch) Returns true if ch is a punctuation character
isspace(ch) Returns true if ch is a whitespace character: space, tab, carriage return, new line, or form feed
isupper(ch) Returns true if ch is an uppercase letter
isxdigit(ch) Returns true if ch is a hexidecimal digit
toascii(ch) Returns ASCII code for ch
tolower(ch) Returns the lowercase version of ch if ch is an uppercase letter; otherwise returns ch
toupper(ch) Returns the uppercase version of ch if ch is a lowercase letter; otherwise returns ch

cfloat (float.h)

Defines named constants that specify the range of floating-point values.

climits (limits.h)

Defines named constants that specify the range of integer values.

cmath (math.h)

The C++ functions in this library compute certain standard mathematical functions. These functions are overloaded to accomodate float, double, and long double. Unless otherwise indicated, each function has one argument, with the return type being the same as the argument type (either float, double, or long double).
acos Returns the arc cosine
asin Returns the arc sine
atan Returns the arc tangent
atan2 Returns the arc tangent x/y for arguments x and y
ceil Rounds up
cos Returns the cosine
cosh Returns the arc cosine
exp Returns ex
fabs Returns the absolute value
floor Rounds down
fmod Returns x modulo y for arguments x and y
frexp For arguments x and eptr, where x = m * 2e, returns m and sets eptr to point to e
ldexp Returns x * 2e , for arguments x and e
log Returns the natural log
log10 Returns the log base 10
modf For arguments x and iptr, returns the fractional part of x and sets iptr to point to the integer part of x
pow Returns xy , for arguments x and y
sin Returns the sine
sinh Returns the hyperbolic sine
sqrt Returns the square root
tan Returns the tangent
tanh Returns the hyperbolic tangent

cstdlib (stdlib.h) 

abort    Terminates program execution abnormally
abs      Returns the absolute value of an integer
atof     Converts a string argument to floating point
atoi     Converts a string argument to an integer
exit     Terminates program execution
rand()   Generates an unsigned int between 0 and RAND_MAX, a named constant
         defined in cstdlib header file
srand(unsigned n)  Seeds the rand() function so that it generates different
         sequences of random numbers.  srand is often used in conjunction
         with the time function from the ctime library.  For example,
         srand(time(0));

cstring (string.h)

This library enables you to manipulate C strings that end in the char '\0', the null char. Unless noted otherwise, these functions return a pointer to the resulting string in addition to modifying an appropriate argument. The argument ch is a character, n is an integer, and the other arguments are strings, which usually means they are names of a char array, but can be string constants in some cases. For example, strcmp("Hello", "Goodbye"); 
strcat(toS, fromS)      Copies fromS to the end of toS
strncat(toS, fromS, n)  Copies at most n characters of fromS to the end
                        of toS and appends \0
strcmp(str1, str2)      Returns an integer that is negative if str1 < str2, 
                        zero if str1 == str2, and positive if str1 > str2
stricmp(str1, str2)     Behaves like strcmp, but ignores case
strncmp(str1, str2, n)  Behaves like strcmp, but compares the first
                        n characters of each string
strcpy(toS, fromS)      Copies fromS toS
strncpy(toS, fromS, n)  Copies n characters of fromS to toS, truncating 
                        or padding with \0 as necessary
strspn(str1, str2)      Returns the number of initial consecutive characters
                        of str1 that are not in str2
strcspn(str1, str2)     Returns the number of initial consecutive characters
                        of str1 that are in str2
strlen(str)             Returns the length of str, excluding \0
strlwr(str)             Converts any uppercase letters in str to lowercase
                        without altering other characters
strupr(str)             Converts any lowercase letters in str to uppercase
                        without altering other characters
strchr(str, ch)         Returns a pointer to the first occurrence of ch 
                        in str; otherwise returns NULL
strrchr(str, ch)        Returns a pointer to the last occurrence of ch in
                        str; otherwise returns NULL
strpbrk(str1, str2)     Returns a pointer to the first character in str1 
                        that also appears in str2; otherwise returns NULL
strstr(str1, str2)      Returns a pointer to the first occurrence of str2
                        in str1; otherwise returns NULL
strtok(str1, str2)      Finds the next token in str1 that is followed by 
                        str2, returns a pointer to the token and writes
                        NULL immediately after the token in str1

ctime

Defines functions for manipulating time and dates.

exception

Defines classes, types, and functions that relate to exception handling. A portion of the class exception is shown below. 
     class exception
     {
     public:
        exception() throw();
        virtual -exception() throw();
        exception &operator=(const exception %exc) throw();
        virtual const char *what() const throw();
     }

fstream (fstream.h)

Declares the C++ classes that support file I/O.

iomanip (iomanip.h)

The manipulation in this library affect the format of steam operations. Note that iostream contains additional manipulators. 
setbase(b)        Setts number base to b = 8, 10, or 16
setfill(f)        Sets fill character to f
setprecision(n)   Sets floating-point precision to integer n
setw(n)           Sets field width to integer n

iostream (iostream.h)

The manipulators in this library affect the format of stream operations. Note that iomanip contains additional manipulators. 
dec               Tells subsequent operation to use decimal representation
end1              Inserts new-line character \n and flushes output stream
ends              Inserts null character \0 in an output stream
flush             Flushes an output stream
hex               Tells subsequent I/O operations to use hexadecimal
                  representation
oct               Tells subsequent I/O operation to use octal representation
ws                Extracts whitespace characters on input stream

string

This library enables you to manipulate C++ strings. Described here is a selection of the functions that this library provides. In addition, you can use the following operators with C++ strings: =, +, ==, !=, <, <=, >, >=, <<, and >>. Note that positions within a string begin at 0. 
erase()                  Makes the string empty
erase(pos, len)          Removes the substring that begins at position pos and
                         contains len characters
find(subString)          Returns the position of a substring within the string
length()                 Returns the number of characters in the string 
                         (same as size)
replace(pos, len, str)   Replaces the substring that begins at position
                         pos and contains len characters with the string str
size()                   Returns the number of characters in ths string
                         (same as length)
substr(pos, len)         Returns the substring that begins at position pos
                         and contains len characters
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