catalogue

1, C language calculates the day of a year

2, Compiling C language program under Linux

 

1, C language calculates the day of a year  

The general idea of this program is: day = (requested date month - 1) * 31 + date of requested date - redundant days (because the days of each month are different, the previous * 31 will make the result a few more days, so it needs to be subtracted)

There are three cases

Month = 1, 2, month < = 7, month > 7

  Month = 1, 2 hours

In both normal and leap years, January and February do not need to subtract "extra days"

Month < = 7:00

"Extra days" = quotient of month month divided by 2 (leap year)

"Extra days" = month - (quotient of month divided by 2 + 1) (normal year)

Month > 7:00

"Extra days" = quotient of month divided by 2 (leap year)

"Extra days" = quotient of month divided by 2 + 1 (normal year)

#include <stdio.h>
void main()
{
	int mm0, mm1, mm2, mm3, mm4, mm5,mm6, mm7,mm8,mm9,day;
	printf("Enter date(8 Digits (example: 20210922):");
	scanf("%d", &mm0);
	mm1 = mm0 / 10000;//particular year
	mm2 = mm0 / 100 % 100;//month
	mm3 = mm0 % 100;//day
	mm4 = mm1 % 4;//Judge whether the leap year is divided by 4
	mm5 = mm2 - 1;//Month minus 1
	mm6 = mm2 / 2;//Quotient of month divided by 2
	mm7 = mm2 - mm6;
	mm8 = mm7 + 1;
	mm9 = mm2 / 2 + 1;
		if (mm4==0)//A leap year is divided by four
		{
			if (mm2 == 2)
			{
				day = mm5 * 31 + mm3;
				printf("%d The second day of the year%d day", mm1, day);
			}
			else if (mm2 <= 7)
			{
				if (mm2 == 1)
				{
					day = mm5 * 31 + mm3;
					printf("%d The second day of the year%d day", mm1, day);
				}
				else
				{
					day = mm5 * 31 + mm3 - mm7;
					printf("%d The second day of the year%d day", mm1, day);
				}
				
			}
			else
			{
				day = mm5 * 31 + mm3 - mm6;
				printf("%d The second day of the year%d day", mm1, day);
			}
		}
		else//Ordinary year
		{
			if (mm2 == 2)
			{
				day = mm5 * 31 + mm3;
				printf("%d The second day of the year%d day", mm1, day);
			}
			else if (mm2 <= 7)
			{
				if (mm2 == 1)
				{
					day = mm5 * 31 + mm3;
					printf("%d The second day of the year%d day", mm1, day);
				}
				else
				{
					day = mm5 * 31 + mm3 - mm8;
					printf("%d The second day of the year%d day", mm1, day);
				}
				
			}
			else
			{
				day = mm5 * 31 + mm3 - mm9;
				printf("%d The second day of the year%d day", mm1, day);
			}
		}
}

In some scientific calculations, it is necessary to calculate the day of a year. For example, in the process of calculating MJD for astronomical observation, the following time format needs to be converted.  

2018-11-26T21:39:19

  Convert it to the following format for the next operation

2018-330-21:39:19

#include <stdio.h>
void main()
{
	int  mm1, mm2, mm3, mm4, mm5, mm6, mm7, mm8, mm9, day, nm1, nm2, nm3;//nm1,nm2,nm3 are time
	printf("Enter date:");
	scanf("%d-%d-%dT%d:%d:%d", &mm1, &mm2, &mm3, &nm1, &nm2, &nm3);
	mm4 = mm1 % 4;//Judge whether the leap year is divided by 4
	mm5 = mm2 - 1;//Month minus one
	mm6 = mm2 / 2;
	mm7 = mm2 - mm6;
	mm8 = mm7 + 1;
	mm9 = mm2 / 2 + 1;
	if (mm4 == 0)//A leap year is divided by four
	{
		if (mm2 == 2)
		{
			day = mm5 * 31 + mm3;
			printf("%d-%d-%d:%d:%d", mm1, day, nm1, nm2, nm3);
		}
		else if (mm2 <= 7)
		{
			if (mm2 == 1)
			{
				day = mm5 * 31 + mm3;
				printf("%d-%d-%d:%d:%d", mm1, day, nm1, nm2, nm3);
			}
			else
			{
				day = mm5 * 31 + mm3 - mm7;
				printf("%d-%d-%d:%d:%d", mm1, day, nm1, nm2, nm3);
			}

		}
		else
		{
			day = mm5 * 31 + mm3 - mm6;
			printf("%d-%d-%d:%d:%d", mm1, day, nm1, nm2, nm3);
		}
	}
	else
	{
		if (mm2 == 2)
		{
			day = mm5 * 31 + mm3;
			printf("%d-%d-%d:%d:%d", mm1, day, nm1, nm2, nm3);
		}
		else if (mm2 <= 7)
		{
			if (mm2 == 1)
			{
				day = mm5 * 31 + mm3;
				printf("%d-%d-%d:%d:%d", mm1, day, nm1, nm2, nm3);
			}
			else;
			{
				day = mm5 * 31 + mm3 - mm8;
				printf("%d-%d-%d:%d:%d", mm1, day, nm1, nm2, nm3);
			}

		}
		else
		{
			day = mm5 * 31 + mm3 - mm9;
			printf("%d-%d-%d:%d:%d", mm1, day, nm1, nm2, nm3);
		}
	}
}

2, Compiling under Linux

Many astronomical data processing tools need to run under Linux, so it is necessary to compile C language programs in Linux. (gcc command is required for this procedure)

1. Create a file named. c (take vim as an example)

vim test.c

2. Paste the code of C language program into test.c file and save it

3. Compilation

gcc day.c -o day

 

 

Finally, a file will be generated and try to run it

./day

 

This concludes the tutorial  

Write at the end

This program comes from students who have just learned C language (only one class, so they can only use simple sentences if, / laugh and cry) and is the first blog post. I will constantly learn to update the program from time to time to make it the simplest. If you have any questions, you can comment or send a private letter. I hope you can give suggestions and hope to communicate with you~