Hãy biến ứng dụng hết sức dài dòng này thành các hàm nhỏ, đọc hiểu chi tiết và

#include<stdio.h>

int main() {
    while (1) {
        int a, b, c, d, e, f, i, j;//,k,l,m,n;
        printf("Chon hinh ma ban muon ve\n");
        printf("0> thoat\n");
        printf("1> hinh vuong dac\n");
        printf("2> hinh vuong rong\n");
        printf("3> hinh vuong cheo\n");
        printf("4> hinh vuong cong\n");
        printf("5> hinh vuong thoi\n");
        scanf("%d", &a);
        if (a == 0)
            break;
        switch (a) {
            case 1:
                printf("Nhap do dai canh hinh vuong: ");
                scanf("%d", &b);
                for (i = 1; i <= b; i++) {
                    for (j = 1; j <= b; j++)
                        printf(" * ");
                    printf("\n\n");
                }
                break;
            case 2:
                printf("nhap do dai canh cua hinh vuong   ");
                scanf("%d", &c);
                if (c < 3) {
                    printf("Khong the in hinh.");
                } else {
                    for (i = 1; i <= c; i++) {
                        for (j = 1; j <= c; j++)
                            if (i == 1 || j == 1 || i == c || j == c) {
                                printf(" * ");
                            } else {
                                printf("   ");
                            }
                        printf("\n\n");
                    }
                }
                break;
            case 3:
                printf("nhap do dai canh cua hinh vuong");
                scanf("%d", &d);
                if (d % 2 == 0 || d < 5) {
                    printf("Khong the in hinh.");
                } else {
                    for (i = 1; i <= d; i++) {
                        for (j = 1; j <= d; j++)
                            if (i == 1 || j == 1 || i == d || j == d || i == j || (i + j) == (d + 1)) {
                                printf(" * ");
                            } else {
                                printf("   ");
                            }
                        printf("\n\n");
                    }
                }
                break;
            case 4:
                printf("nhap do dai canh cua hinh vuong");
                scanf("%d", &e);
                if (e % 2 == 0 || e < 5) {
                    printf("Khong the in hinh.");
                } else {
                    for (int i = 1; i <= e; i++) {
                        for (int j = 1; j <= e; j++)
                            if (i == 1 || i == e || j == 1 || j == e || i == (e + 1) / 2 || j == (e + 1) / 2) {
                                printf(" * ");
                            } else {
                                printf("   ");
                            }
                        printf("\n\n");
                    }
                }
                break;
            case 5:
                printf("nhap do dai canh hinh vuong");
                scanf("%d", &f);
                for (i = 1; i <= (f + 1) / 2; i++) {
                    for (j = 1; j <= f; j++)
                        if (i + j == (f + 1) / 2 + 1 || j - i == (f + 1) / 2 - 1 || j == 1 || j == f || i == 1)
                            printf(" * ");
                        else
                            printf("   ");
                    printf("\n\n");
                }
                for (i = 0; i < (f + 1) / 2; i++) {
                    for (j = 0; j < f; j++) {
                        if (j == 0 || i == (f + 1) / 2 - 1 || (i + j) == f - 1 || j == f - 1 || i == j)
                            printf(" * ");
                        else
                            printf("   ");
                    }
                    printf("\n\n");
                }
        }
    }
}