A few questions

[hjast]

using namespace std;
 
class myString
{
        private:
            char value[20]; // Assume no more than 20 characters for simplicity.
        public:
            myString (char *str) { strcpy (value, str); } // Constructor
            void printString ( ) { cout << value << endl; }
            myString& operator+= (const myString& s1)
            {
            char concString[50];
            strncpy(concString,value,20);
            strncpy(concString,s1.value,20);
            myString finalString(concString);
            *value=*finalString.value;
 
            }
};
 
 
 

 *  myStringMain.cpp
 *
 *  Created by Reuben Doetsch on 10/18/07.
 *  Copyright 2007 __MyCompanyName__. All rights reserved.
 *
 */
 
#include "myString.h"
 
main()
{
char firstString[20];
cout << "Enter String @1:";
cin >> firstString;
 
myString first(firstString);
 
char secondString[20];
cout << "enter string 2:";
cin >> secondString;
 
myString second(secondString);
 
first+=second;
 
first.printString();
}
 

I don't understand why this doesn't work as intended. This is supposed to concate the strings.

[weaknessforcats]

[qute=hjast]
class myString
{
private:
char value[20]; // Assume no more than 20 characters for simplicity.
public:
myString (char *str) { strcpy (value, str); } // Constructor
void printString ( ) { cout << value << endl; }
myString& operator+= (const myString& s1)
{
char concString[50];
strncpy(concString,value,20);
strncpy(concString,s1.value,20);
myString finalString(concString);
*value=*finalString.value;

}
};
[/quote]

I presume this for a class or something since C++ already hjas a string class.

However, your += operator just needs to concatenate the value in s1 to the value in the the this obect. You need ot allow for a null terminator also.

myString& operator+= (const myString& s1)
{
            int len = strlen(this->value);
            strncat(this->value, s1.value, 20 - len -1);
            strcat(this->value, '\0'); ;
 }
 

Your code:

myString finalString(concString);
*value=*finalString.value;

just creates a local variable named finalString followed by an assignment of finalString.value[0] to this->value[0]. This is not a copy of the string. Rather, it's just the assignment of a single character.