4-3

code/practise/06 循环/01 账簿计算/main.c

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+#include<stdio.h>
+
+int main(void) {
+
+	double balance = 0; // 余额
+	double credit, debit;
+
+	// 菜单，形式可以自己设计，尽量美观一点嘛，不过不用纠结这种界面，不要舍本逐末。
+
+	printf("**** ACME checkbook-balancing program ****\n");
+	printf("     Comands:                             \n");
+	printf("             0 = clear                    \n");
+	printf("             1 = credit                   \n");
+	printf("             2 = debit                    \n");
+	printf("             3 = balance                  \n");
+	printf("             4 = exit                     \n");
+
+	// 题目中已经规定了这些功能用 0，1，2，3，4 代替，其实是想让我们用 switch
+	// 如果你想用 if else 也完全 ok
+
+	// 死循环让用户可以重复选择
+	while (1) {
+		int choice;
+		printf("Enter command: ");
+		scanf("%d", &choice);
+		
+		switch (choice) {
+					
+					// 清除账户是一种很“危险”的举动，可以让用户确认一次
+
+			case 0:	printf("Are you sure to clear your balance?\n");
+					printf("1 = yes, 0 = no\n");
+					int isClear;
+					scanf("%d", &isClear);
+					if (isClear == 1) {
+						balance = 0;
+						printf("clear successfully!\n");
+					}					
+					break;
+			
+			case 1: printf("Enter amount of credit: ");
+					scanf("%lf", &credit);
+					balance += credit;
+					break;
+			
+			case 2: printf("Enter amount of debit : ");
+					scanf("%lf", &debit);
+					balance -= debit;
+					break;
+
+			case 3: printf("Current balance: %.2f\n", balance);
+					break;
+					
+			case 4: printf("Are you sure to quit?\n");
+					printf("1 = yes, 0 = no\n");
+					int isQuit;
+					scanf("%d", &isQuit);
+					if (isQuit == 1) {
+						printf("Goodbye~\n");
+						return 0;
+					}
+					else {
+						break;
+					}
+			default: printf("Illeagl option!\n");
+					 break;
+		}
+	}
+}
+

code/practise/06 循环/01 账簿计算/readme.md

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+#### 程序：账薄结算
+
+这个程序帮你理解一种简单的交互式程序设计，我们可以通过这种方式设计菜单。
+
+题目：
+
+开发一个程序用来维护账簿的余额。程序将为用户提供选择菜单：清空余额账户，向账户存钱，从账户取钱，显示当前余额，退出程序。选项用 0，1，2，3，4表示。程序的会话类似这样：
+
+```c
+**** ACME checkbook-balancing program ****
+Comands: 0 = clear, 1 = credit, 2 = debit, 3 = balance, 4 = exit
+
+Enter command: 1
+Enter amount of credit: 1042.56
+Enter command: 2
+Enter amount of debit : 133.56
+Enter command: 3
+Current balance: 909
+Ener command: 4
+Goodbye~
+```
+