无论如何，我可以在此代码中使用自定义函数吗？我的作业要求我使用自定义功能，但是我对此不太擅长，我该怎么做？这是一个收银员程序，要求用户提供他们想要购买的产品的商品代码。
#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
int main(void)
{
int i,j = 0, code, amt, key, lines = 0;
int id[100], stock[100], k = 0;
char name[100][20], product[100], newstock[100];
float price[100], sum;
float total = 0;
char ipname[100][20];
int quantity[100], ch;
float ipprice[100];
float ipsub[100],pay,balance;
FILE *fp1;
fp1 = fopen("Fruit.txt", "r");
if(fp1 == NULL)
{
printf("ERROR in opening file\n");
return 1;
}
else
{
while((ch = getc(fp1))!= EOF)
{
if(ch == '\n')
lines++;
}
}
fclose(fp1);
fp1 = fopen("Fruit.txt","r");
if(fp1 == NULL)
{
printf("ERROR in opening file\n");
return 1;
}
else
{
for(i = 0; i < lines; i++)
{
fgets(product, sizeof(product), fp1);
id[i] = atoi(strtok(product, ","));
strcpy(name[i], strtok(NULL, ","));
price[i] = atof(strtok(NULL, ","));
stock[i]=atoi(strtok(NULL,"\n"));
}
}
fclose(fp1);
FILE *fp3;
fp3 = fopen("Stock.txt", "r");
if(fp3!=NULL)
{
for(i = 0; i < lines; i++)
{
fgets(newstock, sizeof(newstock), fp3);
id[i] = atoi(strtok(newstock, ","));
strcpy(name[i], strtok(NULL, ","));
price[i] = atof(strtok(NULL, ","));
stock[i] = atoi(strtok(NULL, "\n"));
}
}
fclose(fp3);
printf("=============================================================\n");
for(i = 0; i < lines; i++)
{
printf("%d:%-10s\t", i +1, name[i]);
}
printf("\n\n%-5s%-20s%-15s%-10s%s\n", "No.", "Product", "Price", "Quantity", "Subtotal");
printf("%-5s%-20s%-15s%-10s%s\n", "===", "=======", "=====", "========", "========");
do
{
k = 0;
system("cls");
printf("=============================================================\n");
for(i = 0; i < lines; i++)
{
printf("%d:%-10s\t", i +1, name[i]);
}
printf("\n\n%-5s%-20s%-15s%-10s%s\n", "No.", "Product", "Price", "Quantity", "Subtotal");
printf("%-5s%-20s%-15s%-10s%s\n", "===", "=======", "=====", "========", "========");
if(j > 0)
{
for(k = 0; k < j; k++)
{
printf("%-5d%-20sRM%-13.2f%-10dRM%.2f\n", k +1, ipname[k], ipprice[k], quantity[k], ipsub[k]);
}
}
sum = 0;
amt = 0;
printf("\nProduct code:");
scanf("%d", &code);
i = code -1;
if(i < lines && i >= 0)
{
printf("Quantity:");
scanf("%d", &amt);
stock[i] = stock[i] -amt;
system("cls");
sum = price[i] *amt;
total = total + sum;
ipprice[j] = price[i];
strcpy(ipname[j], name[i]);
quantity[j] = amt;
ipsub[j] = sum;
printf("=============================================================\n");
for(i = 0; i < lines; i++)
{
printf("%d:%-10s\t", i +1, name[i]);
}
printf("\n\n%-5s%-20s%-15s%-10s%s\n", "No.", "Product", "Price", "Quantity", "Subtotal");
printf("%-5s%-20s%-15s%-10s%s\n", "===", "=======", "=====", "========", "========");
for(k = 0; k <= j; k++)
{
printf("%-5d%-20sRM%-13.2f%-10dRM%.2f\n", k +1, ipname[k], ipprice[k], quantity[k], ipsub[k]);
}
printf("\nPress ESC on keyboard to finalize the bill or Press any key continue...\n");
j++;
key = _getch();
}
else
{
system("cls");
printf("=============================================================\n");
for(i = 0; i < lines; i++)
{
printf("%d:%-10s\t", i +1, name[i]);
}
printf("\n\n%-5s%-20s%-15s%-10s%s\n", "No.", "Product", "Price", "Quantity", "Subtotal");
printf("%-5s%-20s%-15s%-10s%s\n", "===", "=======", "=====", "========", "========");
if(j > 0)
{
for(k = 0; k < j; k++)
{
printf("%-5d%-20sRM%-13.2f%-10dRM%.2f\n", k +1, ipname[k], ipprice[k], quantity[k], ipsub[k]);
}
}
printf("\nInvalid product code entered, press any key to try again or press esc to finalize bill...\n\n");
}
} while(key != 27);
do
{
system("cls");
printf("=============================================================\n");
for(i = 0; i < lines; i++)
{
printf("%d:%-10s\t",i+1,name[i]);
}
printf("\n\n%-5s%-20s%-15s%-10s%s\n", "No.", "Product", "Price", "Quantity", "Subtotal");
printf("%-5s%-20s%-15s%-10s%s\n", "===", "=======", "=====", "========", "========");
for(k = 0; k < j; k++)
{
printf("%-5d%-20sRM%-13.2f%-10dRM%.2f\n", k +1, ipname[k], ipprice[k], quantity[k], ipsub[k]);
}
printf("\nGrand Total = RM%.2f\n",total);
printf("\nPayment = RM");
scanf("%f", &pay);
if(pay >= total)
{
balance = pay - total;
printf("\nBalance = RM%.2f\n", balance);
}
else
{
printf("\nInsufficient payment, Please enter larger amount!\nPress any key...");
getch();
}
}while(pay < total);
FILE *fp2;
fp2 = fopen("receipt.txt", "w");
if(fp1 == NULL)
{
printf("ERROR in opening file\n");
return 1;
}
time_t now;
time(&now);
fprintf(fp2,"\n\n%-5s%-20s%-15s%-10s%s\n", "No.", "Product", "Price", "Quantity", "Subtotal");
fprintf(fp2,"%-5s%-20s%-15s%-10s%s\n", "===", "=======", "=====", "========", "========");
for(k = 0; k < j; k++)
{
fprintf(fp2,"%-5d%-20sRM%-13.2f%-10dRM%.2f\n", k +1, ipname[k], ipprice[k], quantity[k], ipsub[k]);
}
fprintf(fp2,"\n\nGrand Total = RM%.2f\n", total);
fprintf(fp2,"Payment = RM%.2f\n", pay);
fprintf(fp2,"Balance = RM%.2f\n", balance);
fclose(fp2);
fp3 = fopen("Stock.txt", "w");
if(fp3 == NULL)
{
printf("ERROR in updating stock file\n");
return 1;
}
else
{
for(i = 0; i < lines; i++)
{
fprintf(fp3,"%d,%s,%.2f,%d\n", id[i], name[i], price[i], stock[i])
}
}
fclose(fp1);
return 0;
}
txt文件的内容
18156,Apple,1.49,73
45776,Aprikot,1.59,23
73191,Avocado,2.49,63
72829,Banana,2.99,27
74084,Blueberry,5.49,36
79800,Coconut,3.49,80
16611,Grape,8.99,42
62690,Grapefruit,2.19,34
47089,Guava,4.99,42
70412,Jackfruit,19.99,29
44640,Kiwifruit,2.15,38
94768,Lemon,0.99,42
86240,Mango,3.99,62
78697,Orange,1.69,23
74470,Papaya,4.49,23
23959,Pear,2.49,36
78862,Pineapple,2.99,71
82943,Pomegranate,4.35,19
56180,Pomelo,12.99,72
67712,Starfruit,2.79,59
33974,Strawberry,13.99,31
45584,Watermelon,6.88,21
首先也是最重要的一点是，扔掉笔记，并为自己准备一本不错的C编程书。在《权威C书籍指南和清单》中，您可以找到一个不错的清单，并且可以有个好主意。
只是有关功能的基本概念。尝试一遍又一遍地识别您需要的代码，然后将该代码放入函数中，这样程序将很小，易于理解，而不必再次编写。就像，在您的代码中，我看到了此代码被使用了很多次：
printf("=============================================================\n");
for(i = 0; i < lines; i++)
{
printf("%d:%-10s\t", i +1, name[i]);
}
printf("\n\n%-5s%-20s%-15s%-10s%s\n", "No.", "Product", "Price", "Quantity", "Subtotal");
printf("%-5s%-20s%-15s%-10s%s\n", "===", "=======", "=====", "========", "========");
因此，将其放在这样的函数中：
void PrintNewBillHeader ()
{
printf("=============================================================\n");
for(i = 0; i < lines; i++)
{
printf("%d:%-10s\t", i +1, name[i]);
}
printf("\n\n%-5s%-20s%-15s%-10s%s\n", "No.", "Product", "Price", "Quantity", "Subtotal");
printf("%-5s%-20s%-15s%-10s%s\n", "===", "=======", "=====", "========", "========");
}
然后，无论您在何处执行这些步骤，只需调用此函数PrntNewBillHeader（）即可。简单的。
首先，您正在从文件中读取数据，并且该文件已被调用两次。因此，创建一个新函数ReadFileData（）并将读取代码放入该函数中。但是在这里，您必须传递文件名和要在其中存储数据的数组。因此，将执行以下操作：
int ReadFileData (char * pFileName, char * name, float *pPrice, float *pStock)
{
/**Do declare the variable to be use in this function**/
fp1 = fopen("Fruit.txt","r");
if(fp1 == NULL)
{
return -1;
}
else
{
for(i = 0; i < lines; i++)
{
fgets(product, sizeof(product), fp1);
id[i] = atoi(strtok(product, ","));
strcpy(name[i], strtok(NULL, ","));
price[i] = atof(strtok(NULL, ","));
stock[i]=atoi(strtok(NULL,"\n"));
}
}
fclose(fp1);
return 1;
}
我希望您一定有很多想法。
只需尝试通过一次删除一个冗余代码来拆分主要功能。
希望这可以帮助。
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