Library Mathematical and Date functions in C Language

Library Mathematical Functions

Following are the functions defined in the header math.h −

S.N.	Function & Description
1	double acos(double x) Returns the arc cosine of x in radians.
2	double asin(double x) Returns the arc sine of x in radians.
3	double atan(double x) Returns the arc tangent of x in radians.
4	double atan2(doubly y, double x) Returns the arc tangent in radians of y/x based on the signs of both values to determine the correct quadrant.
5	double cos(double x) Returns the cosine of a radian angle x.
6	double cosh(double x) Returns the hyperbolic cosine of x.
7	double sin(double x) Returns the sine of a radian angle x.
8	double sinh(double x) Returns the hyperbolic sine of x.
9	double tanh(double x) Returns the hyperbolic tangent of x.
10	double exp(double x) Returns the value of e raised to the xth power.
11	double frexp(double x, int *exponent) The returned value is the mantissa and the integer pointed to by exponent is the exponent. The resultant value is x = mantissa * 2 ^ exponent.
12	double ldexp(double x, int exponent) Returns x multiplied by 2 raised to the power of exponent.
13	double log(double x) Returns the natural logarithm (base-e logarithm) of x.
14	double log10(double x) Returns the common logarithm (base-10 logarithm) ofx.
15	double modf(double x, double *integer) The returned value is the fraction component (part after the decimal), and sets integer to the integer component.
16	double pow(double x, double y) Returns x raised to the power of y.
17	double sqrt(double x) Returns the square root of x.
18	double ceil(double x) Returns the smallest integer value greater than or equal to x.
19	double fabs(double x) Returns the absolute value of x.
20	double floor(double x) Returns the largest integer value less than or equal to x.
21	double fmod(double x, double y) Returns the remainder of x divided by y.

Date and Time functions in C

  Time functions in C are used to interact with system time routine and formatted time outputs are displayed. Example programs for the time functions are given below.

S.no	Function	Description
1	setdate()	This function used to modify the system date
2	getdate()	This function is used to get the CPU time
3	clock()	This function is used to get current system time
4	time()	This function is used to get current system time as structure
5	difftime()	This function is used to get the difference between two given times
6	strftime()	This function is used to modify the actual time format
7	mktime()	This function interprets tm structure as calendar time
8	localtime()	This function shares the tm structure that contains date and time informations
9	gmtime()	This function shares the tm structure that contains date and time informations
10	ctime()	This function is used to return string that contains date and time informations
11	asctime()	Tm structure contents are interpreted by this function as calendar time. This time is converted into string.

Example program for setdate() function in C:

This function is used to modify the system date. Please note that other C compilers may not support this setdate() function except turbo C.

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#include<stdio.h> #include<dos.h> #include<conio.h> int main() {    struct date dt;    printf("Enter new date in the format(day month year)");    scanf("%d%d%d",&dt.da_day,&dt.da_mon,&dt.da_year);    setdate(&dt);    printf("Now, current system date is %d-%d-%d\n",dt.da_day,dt.da_mon,dt.da_year);    return 0;   }

Output:

Enter new date in the format (day month year) 01 12 2012 Now, current system date is 01-12-2012

Example program for getdate() function in C:

This function is used to get the CPU time. Please note that other C compilers may not support this getdate() function except turbo C.

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#include<stdio.h> #include<dos.h> int main() {    struct date dt;    getdate(&dt);    printf("Operating system's current date is %d-%d-%d\n"    ,dt.da_day,dt.da_mon,dt.da_year);    return 0; }

Output:

Operating system’s current date is 12-01-2012