conio.h
clrscr( ) Clears text mode window
getch( ) gets a character from console but does not echo to the screen
getche( ) gets a character from console, and echoes to the screen
putch( ) Outputs character to the text window on the screen
cgets( ) Reads string from console
getchar( ) Inputs a character from stdin.
stdlib.h
itoa( ) converts an integer to a string
atoi( ) Converts string of digits to integer
random( ) Returns a random number between 0 and number -1
randomize( ) Initializes random number generator
exit( ) Terminates the program
min( ) Returns the smallest of two numbers
max( ) Returns the largest of two numbers
Itoa( ) converts a long to a string
ultoa( ) converts an unsigned long to a string
atof( ) converts a string to a floating point
atold( ) converts a string to a long double
math.h
abs( ) gets the absolute value of an integer
acos( ) Calculates the inverse of cos Accepts the angle value in radians
asin( ) Calculates the inverse of sin Accepts the angle value in radians
atan( ) Calculates the inverse of tan Accepts the angle value in radians
ceil( ) Returns the largest integer in given list
cos( ) Calculates the cosine Accepts the angle value in radians
cosh( ) Accepts the angle value in radians
exp( ) Calculates the exponent
floor( ) Returns the smallest integer in given list
log( ) Calculates the natural logarithm
log 10( ) Calculates the log of base 10
pow( ) Calculates the power of a number
sin( ) Calculates the sine value of an angle. Accepts the angle value in radians
sqrt( ) Calculates the square root of a number
sqrt( ) Calculates the square root of a number
tan( ) Calculates the tangent value of an angle. Accepts the angle value in radians
tanh( ) Calculates the tangent hyperbolic value
string.h
strcat( ) Function to concatenate(merge) strings
strcmp( ) Function to compare two strings
strcpy( ) Function to copy a string to another string
stricmp( ) Function to compare two strings ignoring their case
strlen( ) Function to calculate the length of the string
strlwr( ) Converts the given string to lowercase
strrev( ) Function to reverse the given string
strupr( ) Converts the given string to uppercase
strdup( ) Duplicates a string
strnicmp( ) Compares the first n characters of one string to another without being case sensitive
strncat( ) Adds the first n characters at the end of second string
strncpy( ) Copies the first n characters of a string into another
strchr( ) Finds the first occurrence of the character
strrchr( ) Finds the last occurrence of the character
strstr( ) Finds the first occurrence of string into another string
strset( ) Sets all the characters of the string to a given character
strnset( ) Sets first n characters of the string to a given character
