Symbol Management Table in C

#include<bits/stdc++.h>

int size=0;
void Insert();
void Display();
void Delete();
int Search(char lab[]);
void Modify();
struct SymbTab
{
    char label[10],symbol[10];
    int addr;
    struct SymbTab *next;
};
struct SymbTab *first,*last;
int main()
{
    int op,y;
    char la[10];
    do
    {
        printf("\n\tSYMBOL TABLE IMPLEMENTATION\n");
        printf("\n\t1.INSERT\n\t2.DISPLAY\n\t3.DELETE\n\t4.SEARCH\n\t5.MODIFY\n\t6.END\n");
        printf("\n\tEnter your option : ");
        scanf("%d",&op);
        switch(op)
        {
        case 1:
            Insert();
            break;
        case 2:
            Display();
            break;
        case 3:
            Delete();
            break;
        case 4:
            printf("\n\tEnter the label to be searched : ");
            scanf("%s",la);
            y=Search(la);
            printf("\n\tSearch Result:");
            if(y==1)
                printf("\n\tThe label is present in the symbol table\n");
            else
                printf("\n\tThe label is not present in the symbol table\n");
            break;
        case 5:
            Modify();
            break;
        case 6:
            exit(0);
        }
    }
    while(op<6);
    getchar();
    return 0;
}
void Insert()
{
    int n;
    char l[10];
    printf("\n\tEnter the label : ");
    scanf("%s",l);
    n=Search(l);
    if(n==1)
        printf("\n\tThe label exists already in the symbol table\n\tDuplicate can’t be inserted");
    else
    {
        struct SymbTab *p = (struct SymbTab*) malloc(sizeof(struct SymbTab));
        strcpy(p->label,l);
        printf("\n\tEnter the symbol : ");
        scanf("%s",p->symbol);
        printf("\n\tEnter the address : ");
        scanf("%d",&p->addr);
        p->next=NULL;
        if(size==0)
        {
            first=p;
            last=p;
        }
        else
        {
            last->next=p;
            last=p;
        }
        size++;
    }
    printf("\n\tLabel inserted\n");
}
void Display()
{
    int i;
    struct SymbTab *p;
    p=first;
    printf("\n\tLABEL\t\tSYMBOL\t\tADDRESS\n");
    for(i=0; i<size; i++)
    {
        printf("\t%s\t\t%s\t\t%d\n",p->label,p->symbol,p->addr);
        p=p->next;
    }
}
int Search(char lab[])
{
    int i,flag=0;
    struct SymbTab *p;
    p=first;
    for(i=0; i<size; i++)
    {
        if(strcmp(p->label,lab)==0)
            flag=1;
        p=p->next;
    }
    return flag;
}
void Modify()
{
    char l[10],nl[10];
    int add,choice,i,s;
    struct SymbTab *p;
    p=first;
    printf("\n\tWhat do you want to modify?\n");
    printf("\n\t1.Only the label\n\t2.Only the address\n\t3.Both the label and address\n");
    printf("\tEnter your choice : ");
    scanf("%d",&choice);
    switch(choice)
    {
    case 1:
        printf("\n\tEnter the old label : ");
        scanf("%s",l);
        s=Search(l);
        if(s==0)
            printf("\n\tLabel not found\n");
        else
        {
            printf("\n\tEnter the new label : ");
            scanf("%s",nl);
            for(i=0; i<size; i++)
            {
                if(strcmp(p->label,l)==0)
                    strcpy(p->label,nl);
                p=p->next;
            }
            printf("\n\tAfter Modification:\n");
            Display();
        }
        break;
    case 2:
        printf("\n\tEnter the label where the address is to be modified : ");
        scanf("%s",l);
        s=Search(l);
        if(s==0)
            printf("\n\tLabel not found\n");
        else
        {
            printf("\n\tEnter the new address : ");
            scanf("%d",&add);
            for(i=0; i<size; i++)
            {
                if(strcmp(p->label,l)==0)
                    p->addr=add;
                p=p->next;
            }
            printf("\n\tAfter Modification:\n");
            Display();
        }
        break;
    case 3:
        printf("\n\tEnter the old label : ");
        scanf("%s",l);
        s=Search(l);
        if(s==0)
            printf("\n\tLabel not found\n");
        else
        {
            printf("\n\tEnter the new label : ");
            scanf("%s",nl);
            printf("\n\tEnter the new address : ");
            scanf("%d",&add);
            for(i=0; i<size; i++)
            {
                if(strcmp(p->label,l)==0)
                {
                    strcpy(p->label,nl);
                    p->addr=add;
                }
                p=p->next;
            }
            printf("\n\tAfter Modification:\n");
            Display();
        }
        break;
    }
}
void Delete()
{
    int a;
    char l[10];
    struct SymbTab *p,*q;
    p=first;
    printf("\n\tEnter the label to be deleted : ");
    scanf("%s",l);
    a=Search(l);
    if(a==0)
        printf("\n\tLabel not found\n");
    else
    {
        if(strcmp(first->label,l)==0)
            first=first->next;
        else if(strcmp(last->label,l)==0)
        {
            q=p->next;
            while(strcmp(q->label,l)!=0)
            {
                p=p->next;
                q=q->next;
            }
            p->next=NULL;
            last=p;
        }
        else
        {
            q=p->next;
            while(strcmp(q->label,l)!=0)
            {
                p=p->next;
                q=q->next;
            }
            p->next=q->next;
        }
        size--;
        printf("\n\tAfter Deletion:\n");
        Display();
    }
}