Как хранить и обновлять строку массива на языке Си ?

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Я хотел сохранить адрес в разделе switch case 7: в программе. когда я нажимаю 7, должен отображаться адрес, который будет ранее сохранен, а также должна быть возможность обновления нового адреса. Но когда я нажимаю 7, ничего не происходит.

Что я уже пробовал:

//Program to display student information
#include<stdio.h>
#include<stdlib.h>
int choice, enrol, batch;

char a[30]={"Any address"};
int i=0;

void main()

{
    do
    {
printf("\n---------------------Student Information Section--------------------------");
printf("\n\n1. Student Information\n");
printf("2. Course Material Despatch Status\n");
printf("3. Fee Status\n");
printf("4. Time Table For Theory Counselling\n");
printf("5. Time Table For Practical Counselling\n");
printf("6. Assignment Submission Schedule\n");
printf("7. Change Of The Correspondence Address\n");
printf("8. General Queries\n");
printf("9. Quit");
printf("-------------------------------------\n\n");
printf("\nEnter your choice: ");
scanf("%d", &choice);

switch (choice)
{
case 1:
while(enrol!=1234)
{
 printf("\nEnter Your Enrolment Number: ");
 scanf("%d", &enrol);
 if (enrol != 1234)
printf("\nPlease Enter a valid Enrolment No.\n");
}

    printf("\n\n********BCA PROGRAMME********");
    printf("\nCourse duration Minimum 3 years Maximum 6 Years");
    printf("\nYear of Study 2017");
    printf("\nRegistered Semester II");
    printf("\nStudy Center Guwahati");
    printf("\nRegional Center Guwahati");
    printf("\nFees paid For Per Semester 6000/-");
    printf("\nBatch No: 5");
    printf("\nClass duration will be one and half an hour");
    break;
case 2:
    printf("\nStudy material is despatched.");
    break;
case 3:
    printf("\nFees is Paid For Semester II: 6000/-");
    break;
case 4:
    while(batch!=5)
{
 printf("\nEnter Your Batch Number: ");
 scanf("%d", &batch);
 printf("\nTheory counselling will start from 9 AM\nPlease visit study centre for complete details.\n");
 if (batch != 5)
printf("\nPlease Enter a valid Batch No.\n");
}
break;
case 5:
    while(batch!=5)
{
 printf("\nEnter Your Batch Number: ");
 scanf("%d", &batch);
 printf("\nPractical counselling will start from 9 AM\nPlease visit study centre for complete details.\n");
 if (batch != 5)
printf("\nPlease Enter a valid Batch No.\n");
}
break;
case 6:
    printf("Last date of submission of assignment");
    printf("\nFor July-December Session is 15th october 2017");
    printf("\nFor January-June Session is 15th April 2018");
break;
case 7:
 while( (a[i++]=getchar()) != '\n' && i < 30) /* take input from user until it's a newline or equal to 30 */
        ;
     a[i] = '\0'; /* null-terminate the string */
     i = 0;
     while(a[i] != '\0') /* print until we've hit \0 */
         printf("%c",a[i++]);

break;
case 8:
    printf("\n---------Frequently Asked Questions-----------");
    printf("\n\n\nQ)What is Academic Schedule?");
    printf("\nAdmission to various programmes of the \nUniversity are open as per the Academic Calendar.");
    printf("\n\nQ)What is the fee Amount & Mode of the Payment?");
    printf("\nYou can pay using online portal or by bank draft.");
    printf("\n\nQ)When will I be notified of my acceptance?");
    printf("\nYou will be notified of your acceptance usually\nwithin two months after the receipt of your application.");
    printf("\n\nQ)What is an auto generated Control Number?");
    printf("\nAn auto generated Control Number is allotted\nprovisionally after submission of online application form.");
    printf("\n\nQ)What if I forget to take printout of Online Application Form after submission?");
    printf("You can download it again from the print application section.\n\n\n");
break;
case 9:
    exit(0);

default:printf("wrong choice\n");
}

}
while(choice>'1' || choice<'9');
}

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