diff --git a/main.cpp b/main.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..12ca94a4e608df8d03e8b6f16b65469bcff006ec
--- /dev/null
+++ b/main.cpp
@@ -0,0 +1,301 @@
+#include<stdio.h>
+#include<math.h>
+#include<string.h>
+#define _CRT_SECURE_NO_WARNINGS
+#define SHOW "* This program will show you displaying the day of the week or the birthday year calenda from caculate with Korean age *\n\n"
+#define PROMPT "Please enter a person's birth date (yyyy mm dd).\nValid input range for the year entry is 0000 ~ 2020: \tex)2020 01 31.\n"
+#define OP "\n\nPlease enter your option (1~4)\n\n"
+#define A "Please enter a desired age. The valid range for the age is 0~120:\n"
+#define E1 "*********************************************************************************\n"
+#define E2 "* *\n"
+#define ERROR "Wrong input, please try again.\n"
+#define PNS "\nPlease enter '-1' for previous month, '1' for next month and '0' for stop\ndisplaying: "
+#define S1 "*\t1. Display the day of the week when the person was born\t\t\t*\n"
+#define S2 "*\t2. Display the day of the week on person's nnth birthday\t\t*\n"
+#define S3 "*\t3. Display the birth month calendar the birth year\t\t\t*\n"
+#define S4 "*\t4. Display the birth month calendar of the person's nnth birthday\t*\n"
+#define DI "\t\t\t This program was made by 202020815, 김영훈\n\n"
+
+void printcal(int y, int m, int ly, int sum);
+void printm(int m);
+int sumofday(int y, int m, int d);
+
+int main() {
+ printf(DI);
+ printf(SHOW);
+ printf(PROMPT);
+ int y, m, d;
+ int age = 0;
+ int num;
+ int ly;
+
+ do {
+ scanf("%4d %2d %2d", &y, &m, &d);
+ if (!((0 <= y && y <= 2020) && (0 < m && m <= 12) && (0 < d && d <= 31))) {
+ printf(ERROR);
+ }
+ else
+ {
+ break;
+ }
+ } while (1);
+
+ printf(E1);
+ printf("\n%d/%d, %d has been entered.\n", m,d,y);
+
+ printf(OP);
+ printf(E1);
+ printf(E2);
+ printf(S1);
+ printf(S2);
+ printf(S3);
+ printf(S4);
+ printf(E2);
+ printf(E1);
+
+ int day_of_ly = ((y - 1) * 365 + ((y - 1) / 4) - ((y - 1) / 100) + ((y - 1) / 400)) % 7;
+ int i;
+
+ do {
+ scanf("%d", &num);
+ if (!(1 <= num && num <= 4)) {
+ printf(ERROR);
+ }
+ else
+ {
+ break;
+ }
+ } while (1);
+
+ int k;
+
+ switch (num)
+ {
+ case 1:
+ k = sumofday(y, m, d) % 7;
+ switch (k)
+ {
+ case 0: printf("This person was born on Sunday.\n");
+ break;
+ case 1: printf("This person was born on Monday.\n");
+ break;
+ case 2: printf("This person was born on Tuesday.\n");
+ break;
+ case 3: printf("This person was born on Wendnedsday.\n");
+ break;
+ case 4: printf("This person was born on Thursday.\n");
+ break;
+ case 5: printf("This person was born on Friday.\n");
+ break;
+ case 6: printf("This person was born on Saturday.\n");
+ break;
+ default:
+ break;
+ }
+ break;
+
+
+ case 2:
+ printf(E1);
+ printf(A);
+ scanf("%d", &age);
+ printf("When you were %d years old, the result was...\n\n", age);
+ k = sumofday(y + age - 1, m, d);
+ ly = ((y + age - 2) * 365 + ((y + age - 2) / 4) - ((y + age - 2) / 100) + ((y + age - 2) / 400)) % 7;
+ k = (k + ly) % 7;
+ switch (k)
+ {
+ case 0: printf("%d years old birthday is Sunday.\n", age);
+ break;
+ case 1: printf("%d years old birthday is Monday.\n", age);
+ break;
+ case 2: printf("%d years old birthday is Tuesday.\n", age);
+ break;
+ case 3: printf("%d years old birthday is Wendnedsday.\n", age);
+ break;
+ case 4: printf("%d years old birthday is Thursday.\n", age);
+ break;
+ case 5: printf("%d years old birthday is Friday.\n", age);
+ break;
+ case 6: printf("%d years old birthday is Saturday.\n", age);
+ break;
+ default:
+ break;
+ }
+ break;
+
+ case 3:
+ printf(S3);
+ printcal(y, m, day_of_ly, sumofday(y, m, d));
+ printf(PNS);
+ while (1)
+ {
+ scanf("%d", &i);
+ if (i == 0) {
+ printf("Program was Eixt\n");
+ break;
+ }
+ else if (i == -1 || i == 1) {
+ m += i;
+ if (m == 13) {
+ m = 1; y++;
+ day_of_ly = ((y - 1) * 365 + ((y - 1) / 4) - ((y - 1) / 100) + ((y - 1) / 400)) % 7;
+ }
+ else if (m == 0) {
+ m = 12; y--;
+ day_of_ly = ((y - 1) * 365 + ((y - 1) / 4) - ((y - 1) / 100) + ((y - 1) / 400)) % 7;
+ }
+ printcal(y, m, day_of_ly, sumofday(y, m, d));
+ printf(PNS);
+ continue;
+ }
+ else
+ printf(ERROR);
+ break;
+ }
+
+ break;
+
+ case 4:
+ printf(E1);
+ printf(S4);
+ printf(A);
+ scanf("%d", &age);
+ printf("When you were %d years old, the result was...\n\n", age);
+ y += age - 1;
+ day_of_ly = ((y - 1) * 365 + ((y - 1) / 4) - ((y - 1) / 100) + ((y - 1) / 400)) % 7;
+ printcal(y, m, day_of_ly, sumofday(y, m, d));
+ printf(PNS);
+ while (1)
+ {
+ scanf("%d", &i);
+ if (i == 0) {
+ printf("Program was Eixt\n");
+ break;
+ }
+ else if (i == -1 || i == 1) {
+ m += i;
+ if (m == 13) {
+ m = 1; y++;
+ }
+ else if (m == 0) {
+ m = 12; y--;
+ }
+ printcal(y, m, day_of_ly, sumofday(y, m, d));
+ printf(PNS);
+ continue;
+ }
+ else
+ printf(ERROR);
+ break;
+ }
+ break;
+
+ }
+ printf("Thanks!\n");
+ return 0;
+
+}
+
+int sumofday(int y, int m, int d) {
+ int rs = 0;
+ switch (m) { //m-1월까지의 요일 합
+ case 12: rs += 30;
+ case 11: rs += 31;
+ case 10: rs += 30;
+ case 9: rs += 31;
+ case 8: rs += 31;
+ case 7: rs += 30;
+ case 6: rs += 31;
+ case 5: rs += 30;
+ case 4: rs += 31;
+ case 3: rs += 28;
+ case 2: rs += 31;
+ case 1:break;
+ default: break;
+ }
+ if (m > 2) {
+ if (y % 4 == 0) {
+ if (y % 100 == 0) {
+ if (y % 400 == 0)
+ rs++;
+ }
+ else
+ rs++;
+ }
+ }
+ rs += d;
+ return rs;
+} //
+void printm(int m) {
+ switch (m) {
+ case 1:printf("January\n");
+ break;
+ case 2:printf("February\n");
+ break;
+ case 3:printf("March\n");
+ break;
+ case 4:printf("April\n");
+ break;
+ case 5:printf("May\n");
+ break;
+ case 6:printf("June\n");
+ break;
+ case 7:printf("July\n");
+ break;
+ case 8:printf("August\n");
+ break;
+ case 9:printf("September\n");
+ break;
+ case 10:printf("October\n");
+ break;
+ case 11:printf("November\n");
+ break;
+ case 12:printf("December\n");
+ break;
+ default:break;
+ }
+}
+void printcal(int y, int m, int ly, int sum) {
+ int tmp = sumofday(y, m, 1) % 7 + ly; //해당하는 월의 1일이 시작되는 날짜 세기용
+ int flag = 0; //1이면 윤년, 0이면 일반
+ if (y % 4 == 0) {
+ if (y % 100 == 0) {
+ if (y % 400 == 0)
+ flag = 1;
+ }
+ else
+ flag = 1;
+ }
+ tmp = tmp % 7;
+ printf("Year: %d\nMonth: ", y);
+ printm(m);
+ printf("SUN MON TUE WED THU FRI SAT\n");
+ if (tmp < 7)
+ for (int i = 0; i < tmp; i++)
+ printf(" ");
+ if (m == 1 || m == 3 || m == 5 || m == 7 || m == 8 || m == 10 || m == 12) //31일인 달 출력
+ for (int i = 1; i < 32; i++) {
+ printf("%4d", i);
+ if ((i + tmp) % 7 == 0)
+ printf("\n");
+ }
+ else if (m == 4 || m == 6 || m == 9 || m == 11) //30일인 달 출력
+ for (int i = 1; i < 31; i++) {
+ printf("%4d", i);
+ if ((i + tmp) % 7 == 0)
+ printf("\n");
+ }
+ else if (m == 2 && flag == 0) //28일인 달 출력
+ for (int i = 1; i < 29; i++) {
+ printf("%4d", i);
+ if ((i + tmp) % 7 == 0)
+ printf("\n");
+ }
+ else
+ for (int i = 1; i < 30; i++) { //29일인 달 출력
+ printf("%4d", i);
+ if ((i + tmp) % 7 == 0)
+ printf("\n");
+ }
+}