คือ ผมเขียนโค้ดภาษาซี เกี่ยวกับปฏิทิน โดยการใส่ ปี คศ และเดือน (เช่น 1996-07) โดยในโค้ดนั้นมีสูตรและฟังก์ชันมากมาย ซึ่งผมไม่ค่อยเข้าใจนัก เนื่องจากได้การช่วยจากอาจารย์ และรุ่นพี่ ซึ่งก็ต่างให้สูตร ให้โค้ดมาปราศจากคำอธิบาย ผมจึงอยากขอให้คนในพันทิปช่วย เขียนอธิบายโค้ดขอผมให้หน่อย จะสอบพรีเซ้นแล้ว รบกวนช่วยหน่อยครับ

#include<stdio.h>
#include<conio.h>
#include<windows.h> //ใส่สี

#define Setcolor(txt,back) SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE), back*16+txt)
#define resetcolor() SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE), 15)

#define N 300 //กำหนดค่าตัวแปรทั่วไป N=300

struct specialday //กำหนดโครงสร้างเป็นวันสำคัญ
{
    int date, month;
    char name[50];

}specialday[N];

void Read()
{
    FILE *fp; //ตัวชี้ตำแหน่งข้อมูลในแฟ้ม มีผลทำให้ตัว  file pointer ชี้ไปที่ตำแหน่งเริ่มต้นของแฟ้มข้อมูลทันที
    fp = fopen("specialday","r"); //(ชื่อแฟ้มข้อมูล,โหมดอ่าน)
    int i;
if( fp != 0 )
    for(i=0;i<N;i++)
        {
            fscanf(fp, "%d/%d ", &specialday.date, &specialday.month); // เป็นฟังก์ชันที่ใช้อ่านข้อมูลจากแฟ้มข้อมูล
            fgets(specialday.name, 100, fp);
        }
    fclose(fp);  //จะให้ค่าเท่ากับ 0 เมื่อปิดไฟล์ได้สำเร็จ
}

void Head()
{
    printf("\n\n\n");Setcolor(12,0);
    printf("   ******  ******  ******  *      ******  **    *  *****    *******  ******\n");Setcolor(15,0);
    printf("   *       *    *  *    *  *      *       * *   *  *    *   *     *  *    *\n");Setcolor(9,0);
    printf("   *       ******  ******  *      ******  *  *  *  *     *  *******  ******\n");Setcolor(15,0);
    printf("   *       *    *  *    *  *      *       *   * *  *    *   *     *  *    *\n");Setcolor(12,0);
    printf("   ******  *    *  *     * *****  ******  *    **  *****    *     *  *     *\n");Setcolor(15,0);
}

void Showday(int date,int month ,int r)
{
    if((date==1&&month==1)||(date==6&&month==4)||(date==13&&month==4)||(date==14&&month==4)
||(date==15&&month==4)||(date==1&&month==5)||(date==5&&month==5)||(date==12&&month==8)
||(date==23&&month==10)||(date==5&&month==12)||(date==10&&month==12)||(date==31&&month==12))
        {
            Setcolor(12,0);
        }
    else if((date==10&&month==1)||(date==13&&month==1)||(date==14&&month==1)||(date==16&&month==1)||(date==17&&month==1)
||(date==18&&month==1)||(date==25&&month==1)||(date==2&&month==2)||(date==3&&month==2)||(date==10&&month==2)||(date==14&&month==2)
||(date==24&&month==2)||(date==25&&month==2)||(date==26&&month==2)||(date==5&&month==3)||(date==8&&month==3)||(date==13&&month==3)
||(date==20&&month==3)||(date==21&&month==3)||(date==22&&month==3)||(date==27&&month==3)||(date==31&&month==3)||(date==1&&month==4)
||(date==2&&month==4)||(date==7&&month==4)||(date==22&&month==4)||(date==8&&month==5)||(date==12&&month==5)||(date==31&&month==5)
||(date==5&&month==6)||(date==8&&month==6)||(date==9&&month==6)||(date==24&&month==6)||(date==26&&month==6)||(date==29&&month==7)
||(date==4&&month==8)||(date==7&&month==8)||(date==16&&month==8)||(date==18&&month==8)||(date==16&&month==9)||(date==19&&month==9)
||(date==20&&month==9)||(date==24&&month==9)||(date==27&&month==9)||(date==1&&month==10)||(date==13&&month==10)||(date==14&&month==10)
||(date==16&&month==10)||(date==19&&month==10)||(date==21&&month==10)||(date==31&&month==10)||(date==14&&month==11)||(date==20&&month==11)
||(date==25&&month==11)||(date==27&&month==11)||(date==1&&month==12)||(date==3&&month==12)||(date==4&&month==12)||(date==16&&month==12)
||(date==25&&month==12)||(date==26&&month==12)||(date==28&&month==12))
        {
            Setcolor(2,0);
        }
    printf("\t %d",date);
    Setcolor(15,0);
}

void Calendar(int year,int month)
{
    int end, d=1;
    int r, c;  //roll and column
    int sum, var; //x แทนวันแรกของปี

    //คำสั่งกำหนดจำนววันในแต่ละเดือน
    if(month==1||month==3||month==5||month==7||month==8||month==10||month==12)
    {
        end=31;
    }
    else if(month==4||month==6||month==9||month==11)
    {
        end=30;
    }
    else
    {
        if((year%4)==0)
        {
            end=29;
            if(year0==0)
            {
                end--;
                if(year%400==0)
                {
                    end++;
                }
            }
        }
        else
        {
            end=28;
        }
    }

    sum=(((((year+(year-1)/4-(year-1)/100+(year-1)/400))%7)+7)%7);    //สุ่มเลขตั้งแต่ -1

    if     (month==2)   {sum=(sum+31)%7;}
    else if(month==3)   {sum=(sum+31+28)%7;}
    else if(month==4)   {sum=(sum+31+28+31)%7;}
    else if(month==5)   {sum=(sum+31+28+31+30)%7;}
    else if(month==6)   {sum=(sum+31+28+31+30+31)%7;}
    else if(month==7)   {sum=(sum+31+28+31+30+31+30)%7;}
    else if(month==8)   {sum=(sum+31+28+31+30+31+30+31)%7;}
    else if(month==9)   {sum=(sum+31+28+31+30+31+30+31+31)%7;}
    else if(month==10)  {sum=(sum+31+28+31+30+31+30+31+31+30)%7;}
    else if(month==11)  {sum=(sum+31+28+31+30+31+30+31+31+30+31)%7;}
    else if(month==12)  {sum=(sum+31+28+31+30+31+30+31+31+30+31+30)%7;}

    if((year%4)==0&&month>2)
    {
        sum=(sum+1)%7;
        if(year0==0)
        {
            sum=(sum+6)%7;
            if(year%400==0)
            {
                sum=(sum+1)%7;
            }
        }
    }

    var=(end+sum)/7;
    if((end+sum)%7>0)
    {
        var++;
    }
    var++;

    printf("\t_____________________________________________________\n\n");

    if      (month==1){printf("\t\t\t      January %d\n",year);}
    else if (month==2){printf("\t\t\t      February %d\n",year);}
    else if (month==3){printf("\t\t\t      March %d\n",year);}
    else if (month==4){printf("\t\t\t      April %d\n",year);}
    else if (month==5){printf("\t\t\t      May %d\n",year);}
    else if (month==6){printf("\t\t\t      June %d\n",year);}
    else if (month==7){printf("\t\t\t      July %d\n",year);}
    else if (month==8){printf("\t\t\t      August %d\n",year);}
    else if (month==9){printf("\t\t\t      September %d\n",year);}
    else if (month==10){printf("\t\t\t     October %d\n",year);}
    else if (month==11){printf("\t\t\t     November %d\n",year);}
    else if (month==12){printf("\t\t\t     December %d\n",year);}
    ;

    printf("\t_____________________________________________________\n\n");

    //printf("\t Sun\tMon\tTue\tWed\tThu\tFri\tSat\n");

    Setcolor(12,0); printf("\tSun");
    Setcolor(14,0); printf("\tMon");
    Setcolor(13,0); printf("\tTue");
    Setcolor(10,0); printf("\tWed");
    Setcolor(4,0); printf("\tThu");
    Setcolor(11,0); printf("\tFri");
    Setcolor(5,0); printf("\tSat\n"); Setcolor(15,0);

    printf("\t_____________________________________________________\n\n");

    for(c=1;c<=var;c++)
    {
        printf("\n");

        if (c>1)
        {
            printf("\n");
        }
        for(r=1;r<=7;r++)
        {
            if(d<=end)
            {
                if(sum>0)
                {
                    printf("\t  ");
                    sum=sum--;
                }
                else if(sum==0)
                {
                    Showday (d,month,r);
                    //printf("\t %d",day);
                    d=d++;
                }
            }
        }
    }

    printf("\t_____________________________________________________\n\n");

    //กำหนดวันสำคัญในแต่ละเดือน
    Setcolor(3,0); printf("\t\t\tShow the relevant Day\n"); Setcolor(15,0);

    if(month==1)
    {
        printf("\n\t 1st : New Year Day\n\t 10th: Children's Day\n\t 13rd: National Aviation Day");
        printf("\n\t 14th: Day of National Forest Conservation\n\t 16th: Teacher's Day\n\t 17th: King Ramkhamhaeng's Day");
        printf("\n\t 18th: Army's Day\n\t");
    }
    if(month==2)
    {
        printf("\n\t 2nd : National Argicuture Day\n\t 3th : Veterans Day\n\t 10th: Volunteer Guard Day");
        printf("\n\t 14th: Valentine's Day\n\t 24th: Day of National Artists\n\t 25th: Day of National Radio");
        printf("\n\t 26th: National Cooperative Day");
    }
    if(month==3)
    {
        printf("\n\t 5th : Day of Journalists\n\t 8th : International Women's Day\n\t 13rd: Day of Chang Thailand");
        printf("\n\t 20th: National Volunteer Day\n\t 21st: International Poetry Day\n\t 22nd: Day of World Water Conservation");
        printf("\n\t 27th: Day of Commemorati Air force\n\t 31st: Day of King Nang Kloa");
    }
    if(month==4)
    {
        printf("\n\t 1st : Thailand's Government Savings Day\n\t 2nd : Heritage Conservation Day\n\t 6th : Chakri Day");
        printf("\n\t 7th : World Health Days\n\t 13rd-15th: Songkran Festival\n\t 22nd: Earth Day");
    }
    if(month==5)
    {
        printf("\n\t 1st : Labour Day\n\t 5th : Coronation Day\n\t 8th : International Red Cross Day");
        printf("\n\t 12nd: International Nursing Day\n\t 31st: World No Tobacco Day ");
    }
    if(month==6)
    {
        printf("\n\t 5th : World Environment Day\n\t 8th : World Ocean Day\n\t 9th : VIII's Day");
        printf("\n\t 24th: Day of Rule Change\n\t 26th: Soonthornphu's day");
    }
    if(month==7)
    {
        printf("\n\t 29th: National Day in Thailand");
    }
    if(month==8)
    {
        printf("\n\t 4th : National Communication Day\n\t 7th : Day of LTD.\n\t 12th: Mother Day");
        printf("\n\t 16th: Peace of Thailand Day\n\t 18th: National Science Day");
    }
      if(month==9)
    {
        printf("\n\t 16th: World Ozone Day\n\t 19th: Day of Museum Thailand\n\t 20th: National Youth Day\n\t 24th: Mahidol Day");
    }
    if(month==10)
    {
        printf("\n\t 1st : International Day for Older Persons\n\t 13rd: Police Day\n\t 14th: Democracy Day");

        printf("\n\t 16th: World Food Day\n\t 19th: Technology Day in Thailand\n\t 21st: Social Worker's Day");

        printf("\n\t 23th: Day of Commemoration\n\t 31st: Halloween Day");
    }
    if(month==11)
    {
        printf("\n\t 14th: Day of King's Rain\n\t 20th: Navy Day\n\t 25th: Day of Ementary\n\t 27th: National Day ");
    }
    if(month==12)
    {
        printf("\n\t