Design and implement a program to perform editing operations on a line of text. Your editor should be able to locate a specified target substring, delete a substring, and insert a substring at a specified location. The editor should expect source strings of less than 80 characters.
Here is what I have so far but I can't get it to run.  

#include <stdio.h>
#include<string.h>
#include <ctype.h>

//Defines
#define MAX_LEN 80
#define NOT_FOUND -1
int index = 0;
int n = 0;
const char to_insert;
const char to_find;

char *delete(char *source, int index, int n);
char *do_edit(char *source, char command);
char get_command(void);
char *insert(char *source, const char *to_insert, int index);
int pos(const char *source, const char *to_find);

int main(void)
{
   char source[MAX_LEN], command;
   printf("Enter the source string: >");
   gets(source);

   for (command = get_command();
       command != 'Q';
       command = get_command())
   {
       do_edit(source, command);
       printf("New Source %s", source);
   }
   printf("String after editing is: %s", source);
   return(0);
   {
       char rest_str[MAX_LEN];
       if (strlen(source) <= index + n)
       {
           source[index] = '0';
       }
       else
       {
           strcpy(rest_str, &source[index + n]);
           strcpy(&source[index], rest_str);
       }
       return(source);
   }
   {
       char str[MAX_LEN];
       int index;

       switch (command)
       {
       case 'D':
           printf("String to delete");
           gets(str);
           index = pos(source, str);
           if (index == NOT_FOUND)
               printf("'%s' not found,str");
           else
               delete(source, index, strlen(str));
           break;
       case 'I':
           printf("String to insert: ");
           gets(str);
           printf("Position of insertion is ");
           scanf("%d", &index);
           insert(source, str, index);
           break;
       case 'F':
           printf("String to find: ");
           gets(str);
           index = pos(source, str);
           if (index == NOT_FOUND)
               printf("'%s' is not found at position %d", str, index);
           break;
       default:
           printf("Invalid Edit Command '%c'", command);
       }
       return(source);
   }
   {
       char command, ignore;

       printf("Enter (D)elete,(I)nsert,(F)ind,or (Q)uit ");
       scanf("'%c'", &command);

       do
           ignore = getchar();
       while (ignore != '');

       return (toupper(command));

   }
   {
       char rest_str[MAX_LEN];
       if (strlen(source) <= index)
       {
           strcat(source, to_insert);
       }
       else
       {
           strcpy(rest_str, &source[index]);
           strcpy(&source[index], to_insert);
           strcat(source, rest_str);
       }
       return(source);
   }
   {
       int i = 0, find_len, found = 0, position;
       char substring[MAX_LEN];

       find_len = strlen(to_find);
       while (NOT_FOUND && i <= strlen(source) - find_len)
       {
           strcpy(substring, &source[i], find_len);
           substring[find_len] = '0';

           if (strcmp(substring, to_find) == 0)
               found = 1;
           else
               ++i;
       }
       if (found)
           position = i;
       else
           position = NOT_FOUND;
       return(position);
   }
}

this is in C.