#include<iostream.h>
#include<stdlib.h>
#include<stdio.h>
 
char encrypt(char c)
{
        FILE *fp1, *fp2;
        char ascii;
        fp1 = fopen("subtable.txt","r");
        fp2 = fopen("encrypted.txt","w");
//i need the code or right function here to get the character's or parameter's (char c) ascii code value from the subtable..
//for example, from the main program, a file to be encrypted will be read using fgetc()..fgetc reads single character from a stream that's why we uses a loop to read all characters until the end of file (EOF)..letter A is the first character to be read in file.txt..By calling fgetc() and encrypt(), letter A will be the parameter of function encrypt()..The question is, how could i get its ascii code value from the subtable..
//lettet 'A' should be returned as 'kEm'
        return ascii;
}
char decrypt(char ascii)
{
        FILE *fp;
        char c;
        fp = fopen("encrypted.txt","r");
//from this time, ascii is now the parameter..we're gonna get its character value from the subtable to decrypt it..
        return c;
}
void main(void)
{
        FILE *fp1, *fp2;
        int choice;
        char c, encfname[50], decfname[50];
        cout<<"Please choose (1 - Encrypt || 2 - Decrypt): ";
        cin>>choice;
        switch(choice)
        {
                case 1:
                        cout<<"Enter filename where to save the encrypted one: ";
//for example, enter encrypted.txt
                        cin>>encfname;
                        fp1 = fopen("file.txt","r");
                        fp2 = fopen(encfname,"w");
                        c = fgetc(fp1);
                        while(c!=EOF)
                        {
                                fputc(encrypt(c),fp2);
                        c = fgetc(fp1);
                        }
						break;
                case 2:
                        cout<<"Enter filename where to save the decrypted one: ";
                        cin>>decfname;
                        fp1 = fopen("encrypted.txt","r");
                        fp2 = fopen(decfname,"w");
                        c = fgetc(fp1);
                        while(c!=EOF)
                        {
                                fputc(decrypt(c),fp2);
                        c = fgetc(fp1);
                        }
						break;
         }
}

 
map<char,int> mymap;
map<char,int>::iterator it;
 
mymap['a'] = 0;
 mymap['b'] = 1;
 mymap['c'] = 2;
 mymap['d'] = 3;
 mymap['e'] = 4;
 mymap['f'] = 5; 
 
 
do
{
for ( it=mymap.begin() ; it != mymap.end(); it++ )
 
    {
        if( s[i] == (*it).first )        // s[i] holds the plain text which is     
        {                                     //mapped  to the 1st element of map
            enc[i++] = (*it).second;    // if it matches then the equivalent is 
            len--;                                // is stored in ur enc[] which is the 
          }                                    //encrypted array
 
    }
} while (len != 0);