C programming

#include #include #include #include struct student { char roll[6]; char name[10]; float mark; struct student *next; }*head,*tail; void showinfo(); void insert(); void display(); void pop(); void main() { int x=0; char ch; clrscr(); printf("\n1. Insert a new student."); printf("\n2. Display all students information."); printf("\n3. Remove an existing student."); printf("\n4. Show student information."); printf("\n5. Exit\n"); while(x==0) { printf("Please enter what you want to do(1,2,3,4,5);"); ch=getch(); switch(ch) { case'1': insert(); break; case'2': display(); break; case'3': pop(); break; case'4': showinfo(); break; case'5': x=1; break; } } getch(); } void insert() { struct student *sptr,*aux,*prev; sptr=(struct student*)malloc(sizeof(struct student)); int a,count=1; float mr; printf("\n Enter information to be inserted:\n\n Student roll:"); scanf("%s",sptr->roll); printf("\n Student Name:"); scanf("%s",sptr->name); printf("\n Student gpa:"); scanf("%f",&mr); sptr->mark=mr; sptr->next=NULL; aux=head; if(!head) { head=sptr; tail=sptr; } else { printf("\nEnter the position:"); scanf("%d",&a); while(aux){ if(count==a) break; else prev=aux; count++; aux=aux->next; } if(prev->next==NULL&&a!=1){ tail->next=sptr; tail=sptr; tail->next=NULL; } else{ prev->next=sptr; prev=sptr; prev->next=aux; if(a==1) head=prev; } } } void display() { int c=0; struct student *sptr; sptr=head; if(!sptr) printf("\n\n\nEmpty list-----------Press any key"); printf("\n\n"); if(sptr) printf("\nContents of the list are: "); while(sptr) { c++; printf("\n%d. %s",c,sptr->roll); sptr=sptr->next; } printf("\n\n\nPress any key to continue-----------"); } void pop() { struct student *sptr,*prev; char roll[10]; printf("\nDo you want to remove the roll"); scanf("%s",roll); sptr=head; while(sptr) { if(!strcmp(sptr->roll,roll)) break; else prev=sptr; sptr=sptr->next; } if(sptr) { if(sptr==head) head=sptr->next; if(sptr==tail) { prev->next=NULL; tail=prev; } prev->next=sptr->next; printf("\n The student with roll:%s... is removed",roll); printf("\n\n\nPress any key to continue."); free(sptr); } else printf("\nThe student with roll:%s... is not found.",roll); } void showinfo() { struct student *sptr,*prev; char roll[6]; printf("\nInseart the roll which you want to show info:"); scanf("%s",roll); sptr=head; while(sptr) { if(!strcmp(sptr->roll,roll)) break; sptr=sptr->next; } if(sptr) { printf("\nThe information about student %s is: \n",roll); printf("\nroll= %s name= %s mark=%0.2f",sptr->roll,sptr->name,sptr->mark); printf("\n\n\nPress any key to continue."); free(sptr); } else printf("\nThe student with roll:%s... is not found.",roll); }