1. Library: It is a collection of files that your programs may use called header files. Header files
provide function prototypes, definitions of library functions, data types and constants.
2. Header files:
a. stdio.h: Defines types and macros for standard I/O package. Also defines I/O
b. String.h: Declares several string manipulation and memory manipulation routines. All
functions starting with str and mem
c. Math.h: Declares prototypes for math functions and math error handlers. The routines
perform mathematical calculations and conversions.
d. Stdlib.h: Declares several commonly used routines like conversion routines,
search/sort routines and other miscellaneous things. Ex: free, labs, atof, atoi, atoll.
e. Iostream.h: Declares basic C++ streams I/O routines. Ex: open, close, get, write.
f. Iomanip.h: Declares C++ streams I/O manipulators and contains macros for creating
parameterised manipulators. Ex: dec, endl, ends, hex, oct.
3. Character functions:
a. Isalnum: Returns non zero if arg is letter or digit. Ex: if(isalnum(ch)) cout<<Alpha;
b. Isalpha: returns non zero if ch is an alphabet.
c. Isdigit: Returns non zero if ch is digit.
d. Islower: returns non zero if ch is a lowercase letter
e. Isupper: Returns non zero if ch is uppercase letter
f. Toupper: Returns uppercase equivalent of ch
g. Tolower: Returns lowercase equivalent of ch
4. String functions:
a. Strcat(str2, str1): Concatenates a copy of str2 to str1 and terminates str1 with a null.
b. Strcmp(str2,str1): Compares two strings and returns –ve value if str1<str2 and
positive value if str1>str2
c. Strcpy(str1,str2): Copies contents of str2 to str1
d. Strlen(str): Returns length of null terminated string. Null is not counted.
5. Math functions:
a. Fabs(x): returns absolute value of floating point number
b. Modf(x,y): returns the remainder of x/y.
6. Random and Randomize functions: Two macros of stdlib.h having similar functioning as
rand() and srand()
a. Random: Generates a random number within range 0 to number – 1.
b. Randomize: It initializes or seeds the random number generator with a random