xmas.c

#include <stdio.h>

void putcharn(char character, int i) {
    for(int x = 0; x < i; x++) {
        putchar(character);
    }
}

int main(int argc, char *argv[]) {
    int treeWidth = 7;

    if (argc > 1) {
        sscanf(argv[1], "%d", &treeWidth);
    }

    for (int i = 1; i <= treeWidth; i += 2) {
        putcharn(' ', (treeWidth - i) / 2);
        putcharn('*', i);
        putchar('\n');
    }

    putcharn(' ', (treeWidth-1) / 2);
    printf("|\n");
    printf("* Merry Christmas, and a happy New Year! *\n");
}