Description
By using C++, there is a possibility of setting the date and time. But, C++ standard library does not support date type. So, C++ inherits the properties of functions and structures from C- library and exhibits the settings of CPP Date and Time.
The header file required to set CPP Date and Time is
The last term tm will be in structure format which consists of following elements.
<ctime> or <time.h>.
Mainly, there are four time related types.They are:
The first three terms acts as functions and helps in showing the CPP Date and Time in the form of integer. Some of the functions included in C and C++ standard libraries are given in the below table.
- time_t
- clock_t
- size_t
- struct tm
| Functions | Description |
|---|---|
| time_t time(time_t *time); | Returns local time by converting time_t using pointer |
| char *ctime(const time_t *time); | Returns local time by converting time_t using pointer |
| struct tm *localtime(const time_t *time); | Returns to tm structure using pointer to represent local time |
| clock_t clock(void) | Returns duration of current running program |
| char * asctime(const struct tm * time); | Returns pointer to structure converting the data to day month date hours:minutes:seconds:year\n\0 format |
| struct tm * gmtime(const time_t *time); | Returns pointer to structure representing the GMT time |
| time_t mktime(struct tm *time); | Returns the exact time in the structure when pointer points it. |
| double difftime(time_t time2, time_t time1); | Calculates the differences between time1 and time2 |
| size_t strftime(); | Returns formatted date and time |
| Field | Type | Meaning | Range |
|---|---|---|---|
| tm_sec | int | represents seconds of minutes | 0-61 |
| tm_min | int | represents minutes of hour | 0-59 |
| tm_hour | int | represents hours of day | 0-23 |
| tm_mday | int | represents day of month | 1-31 |
| tm_mon | int | represents month of year from January | 0-11 |
| tm_year | int | represents years since 1900 | |
| tm_wday | int | represents days since Sunday | 0-6 |
| tm_yday | int | represents days since January 1st | 0-365 |
| tm_isdst | int | represents hours saving day time |
Examples
[c]
/*Program to show current date and time using functions*/
#include<iostream>
#include<ctime>
using namespace std;
int main( )
{
// current date/time based on current system
time_t s = time(0);
char* c = ctime(&s);
cout << "The system local date and time is: " << c << endl;
/* converting 's' to tm struct for UTC*/
tm *gmt = gmtime(&s);
c = asctime(gmt);
cout << "The UTC date and time is:" << c << endl;
}[/c]
Output
[c]
The local date and time is: Wed Nov 25 11:42:33 2015
The UTC date and time is:Wed Nov 25 19:42:33 2015[/c]
Example to show current time using struct tm
[c]
#include <iostream>
#include <ctime>
using namespace std;
int main( )
{
time_t s = time(0);
cout << "Number of seconds since January 1,1970:" << s << endl;
tm *loctm = localtime(&s);
cout << "Year: " <<: << 1900 + loctm->tm_year << endl;
cout << "Month: "<< 1 + loctm->tm_mon<< endl;
cout << "Day: "<< loctm->tm_mday << endl;
cout << "Time: "<< 1 + loctm->tm_hour << ":";
cout << 1 + loctm->tm_min << ":";
cout << 1 + loctm->tm_sec << endl;
}[/c]
Output
[c]
Number of seconds since January 1,1970:1448483759
Year: 2015
Month: 11
Day: 25
Time: 13:36:60[/c]
Example
Another example to make default timer
[c]
/*Program to make a timer using C++*/
#include<iostream>
#include<windows.h>
#include<unistd.h>
#include<cstdlib>
using namespace std;
int main( )
{
int sec=0;
int min=0;
int hour=0;
while(true)
{
sleep(1);
sec=sec+1;
if(sec==60)
{
min=min+1;
sec=0;
return 0;
}
if(min == 60)
{
hour=hour+1;
min=0;
}
cout <<hour << " hours "<< min << " minutes " << " and "<< sec << " seconds "<<endl;
}
}[/c]
Output
[c]
0 hours 0 minutes and 1 seconds
0 hours 0 minutes and 2 seconds
0 hours 0 minutes and 3 seconds
0 hours 0 minutes and 4 seconds
0 hours 0 minutes and 5 seconds
.
.
.
.
0 hours 0 minutes and 59 seconds
[/c]
The timer goes on if return statement is not given in the first 'if' loop.
Description
Numbers in C++ will be declared using various data types like short int, int, float, double, long double. These data types are clearly mentioned in previous chapters.
Example
[c]#include<iostream>
using namespace std;
int main ()
{
//Number declarations
short a;
int b;
long c;
float d;
double e;
short f;
//Number initializations
a = 1595959959;
b = 20;
c = 2500000;
d = 515.25;
e = 58958.438;
f = 1595959959;
cout << "short a :" << a << endl;
cout << "int b :" << b << endl;
cout << "long c :" << c << endl;
cout << "float d :" << d << endl;
cout << "double e :" << e << endl;
cout << "short f :" << f << endl;
return 0;
}[/c]
Output:
[c]short a :27287
int b :20
long c :2500000
float d :515.25
double e :58958.4
short f :27287[/c]
Functions
In C++, there is a possibility to perform mathematical operations on numbers.
| Syntax | Description |
|---|---|
| data_type sin(number); | Returns the sine angle to the given number |
| data_type cos(number); | Returns the cosine angle to the given number |
| data_type tan(number); | Returns the tangent angle to the given number |
| data_type log(number); | Returns the logarithm to the given number |
| data_type pow(number1, number2); | The first is a base number and the second is the power |
| data_type hypo(number1, number2); | Returns the length of the hypotenuse in which both numbers represents the sides of right angled triangle |
| data_type sqrt(number); | Returns the square root of the given number |
| data_type abs(number); | Returns the absolute value to the given integer number |
| data_type fabs(number); | Returns the absolute value of any given decimal number |
| data_type floor(number); | Checks the integer which is less than or equal to the argument passed to it |
Example
[c]
#include <iostream>
#include <cmath>
using namespace std;
int main ()
{
// number definition:
short s = 1;
int i = -1000;
long l = 100000;
float f = 230.47;
double d = 200.374;
double x= sin(s);
// mathematical operations;
cout << "sin(d) : " << sin(d) << endl;
cout << "abs(i) : " << abs(i) << endl;
cout << "floor(d) : " << floor(d) << endl;
cout << "sqrt(f) : " << sqrt(f) << endl;
cout << "pow( d, 2) : " << pow(d, 2) << endl;
cout << "value of x: " << x << endl;
return 0;
}[/c]
Output:
[c]
sin(d) : -0.634939
abs(i) : 1000
floor(d) : 200
sqrt(f) : 15.1812
pow( d, 2) : 40149.7
value of x: 0.841471[/c]
Description
Sometimes, there will be need to see random numbers as the output in probability and statistic applications. This is possible by using C++ by using rand() and srand() functions.
<cstdlib> header file is the header file used to generate random numbers.
rand_max is the maximum constant value while using random numbers.
Example
[c]
#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
int main ()
{
int x,y;
srand( (unsigned)time( NULL ) );
for( x = 0; x < 10; x++ )
{
y= rand();
cout <<" Random Numbers are "<< y << endl;
}
return 0;
}[/c]
Output:
[c]
Random Numbers are 11371
Random Numbers are 3585
Random Numbers are 7758
Random Numbers are 27692
Random Numbers are 27765
Random Numbers are 15197
Random Numbers are 30479
Random Numbers are 17323
Random Numbers are 13292
Random Numbers are 8539[/c]
Key Points
CPP Date and Time chapter draws out following important points.
- CPP Date and Time functions use <time.h> header file.
- time_t, clock_t and size_t used to set time.
- Numbers use primitive data types.
- rand() and srand() functions will be used to find random numbers.
- Range of random numbers is 0 and Rand_Max.
Programming
Tips
Be careful while converting local time to GMT and vice-versa.
rand() and srand() functions never throws an exception.