one_month_calendar.c

#include <stdio.h>


int main(void) {
    int days, starting_day;

    printf("Enter number of days in month: ");
    scanf("%d", &days);

    printf("Enter starting day of the week (1=Sun, 7=Sat): ");
    scanf("%d", &starting_day);

    for (int i = 1; i < days + starting_day; ++i) {
        if (i - starting_day >= 0) {
            printf("%d", i - starting_day + 1);
        }

        if (i % 7 == 0) {
            printf("\n");
        } else {
            printf("\t");
        }
    }
}