以下C代码有什么问题。当我编译它时，它表示无法访问的代码。我正在使用Turbo C ++ [英] What is the problem with following C code..It states Unreachable code when I compile it..I am using Turbo C++

问题描述

#include <stdio.h> ///for input output functions like printf, scanf
#include <stdlib.h>
#include <conio.h>
#include <string.h>  ///string operations


/**
    function : gotoxy
    @param input: x and y coordinates
    @param output: moves the cursor in specified position of console
*/


/** Main function started */

int main()
{
    FILE *fp, *ft; /// file pointers
    char another, choice;

    /** structure that represent a employee */
    struct emp
    {
	char name[40]; ///name of employee
	int age; /// age of employee
	float bs; /// basic salary of employee
    };

    struct emp e; /// structure variable creation

    char empname[40]; /// string to store name of the employee

    long int recsize; /// size of each record of employee

    /** open the file in binary read and write mode
    * if the file EMP.DAT already exists then it open that file in read write mode
    * if the file doesn't exit it simply create a new copy
    */
    fp = fopen("EMP.DAT","rb+");
    if(fp == NULL)
    {
	fp = fopen("EMP.DAT","wb+");
	if(fp == NULL)
	{
	    printf("Connot open file");
	    exit(1);
	}
    }

    /// sizeo of each record i.e. size of structure variable e
    recsize = sizeof(e);

    /// infinite loop continues untile the break statement encounter
    while(1)
    {
	system("cls"); ///clear the console window
	gotoxy(30,10); /// move the cursor to postion 30, 10 from top-left corner
	printf("1. Add Record"); /// option for add record
	gotoxy(30,12);
	printf("2. List Records"); /// option for showing existing record
	gotoxy(30,14);
	printf("3. Modify Records"); /// option for editing record
	gotoxy(30,16);
	printf("4. Delete Records"); /// option for deleting record
	gotoxy(30,18);
	printf("5. Exit"); /// exit from the program
	gotoxy(30,20);
	printf("Your Choice: "); /// enter the choice 1, 2, 3, 4, 5
	fflush(stdin); /// flush the input buffer
	choice  = getche(); /// get the input from keyboard
	switch(choice)
	{
	case '1':  /// if user press 1
	    system("cls");
	    fseek(fp,0,SEEK_END); /// search the file and move cursor to end of the file
	    /// here 0 indicates moving 0 distance from the end of the file

	    another = 'y';
	    while(another == 'y')  /// if user want to add another record
	    {
		printf("\nEnter name: ");
		scanf("%s",e.name);
		printf("\nEnter age: ");
		scanf("%d", &e.age);
		printf("\nEnter basic salary: ");
		scanf("%f", &e.bs);

		fwrite(&e,recsize,1,fp); /// write the record in the file

		printf("\nAdd another record(y/n) ");
		fflush(stdin);
                another = getche();
            }
            break;
        case '2':
            system("cls");
            rewind(fp); ///this moves file cursor to start of the file
            while(fread(&e,recsize,1,fp)==1)  /// read the file and fetch the record one record per fetch
            {
                printf("\n%s %d %.2f",e.name,e.age,e.bs); /// print the name, age and basic salary
            }
            getch();
            break;

        case '3':  /// if user press 3 then do editing existing record
            system("cls");
            another = 'y';
            while(another == 'y')
            {
                printf("Enter the employee name to modify: ");
                scanf("%s", empname);
                rewind(fp);
                while(fread(&e,recsize,1,fp)==1)  /// fetch all record from file
                {
                    if(strcmp(e.name,empname) == 0)  ///if entered name matches with that in file
                    {
                        printf("\nEnter new name,age and bs: ");
                        scanf("%s%d%f",e.name,&e.age,&e.bs);
                        fseek(fp,-recsize,SEEK_CUR); /// move the cursor 1 step back from current position
                        fwrite(&e,recsize,1,fp); /// override the record
                        break;
                    }
                }
                printf("\nModify another record(y/n)");
                fflush(stdin);
                another = getche();
            }
            break;
        case '4':
            system("cls");
            another = 'y';
            while(another == 'y')
            {
                printf("\nEnter name of employee to delete: ");
                scanf("%s",empname);
                ft = fopen("Temp.dat","wb");  /// create a intermediate file for temporary storage
                rewind(fp); /// move record to starting of file
                while(fread(&e,recsize,1,fp) == 1)  /// read all records from file
                {
                    if(strcmp(e.name,empname) != 0)  /// if the entered record match
                    {
                        fwrite(&e,recsize,1,ft); /// move all records except the one that is to be deleted to temp file
                    }
                }
                fclose(fp);
                fclose(ft);
                remove("EMP.DAT"); /// remove the orginal file
                rename("Temp.dat","EMP.DAT"); /// rename the temp file to original file name
                fp = fopen("EMP.DAT", "rb+");
                printf("Delete another record(y/n)");
                fflush(stdin);
                another = getche();
            }
            break;
        case '5':
            fclose(fp);  /// close the file
            exit(0); /// exit from the program
        }
    }
    return 0;
}

推荐答案

返回0; 最后将永远不会执行，因为你退出程序时使用退出（0）; （或退出（1）; 如果文件出错了... ...

The return 0; at the end will never be executed, as you are exiting the program with the exit(0); (or exit(1); if something with the file went wrong)...

问题是最终的返回0 行无法执行，因为没有办法退出它上面的while循环。

结果，它不会编译，因为它假定（正确地）你不打算创建一个无限循环然后之后回来。



并帮自己一个忙，并始终如一地缩进你的代码！它使阅读更容易，特别是当你不知道代码或正在寻找这样的问题时。

The problem is that the final return 0 line can't be executed, because there is no way to exit the while loop above it.
As a result, it won't compile, because it assumes (rightly) that you didn't intend to create an infinite loop and then return after it.

And do yourself a favour and indent your code consistently! It make it a lot easier to read, especially when you don't know the code, or are looking for problems like this.

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