contract StandardToken is TokenInterface {


    // token ownership
    mapping (address => uint256) balances;

    // spending permision management
    mapping (address => mapping (address => uint256)) allowed;
    
    
    
    function StandardToken(){
    }
    
    
    /**
     * transfer() - transfer tokens from msg.sender balance 
     *              to requested account
     *
     *  @param to    - target address to transfer tokens
     *  @param value - ammount of tokens to transfer
     *
     *  @return - success / failure of the transaction
     */    
    function transfer(address to, uint256 value) returns (bool success) {
        
        
        if (balances[msg.sender] >= value && value > 0) {

            // do actual tokens transfer       
            balances[msg.sender] -= value;
            balances[to]         += value;
            
            // rise the Transfer event
            Transfer(msg.sender, to, value);
            return true;
        } else {
            
            return false; 
        }
    }
    
    

    
    /**
     * transferFrom() - 
     *
     *  @param from  - 
     *  @param to    - 
     *  @param value - 
     *
     *  @return 
     */
    function transferFrom(address from, address to, uint256 value) returns (bool success) {
    
        if ( balances[from] >= value && 
             allowed[from][msg.sender] >= value && 
             value > 0) {
                                          
    
            // do the actual transfer
            balances[from] -= value;    
            balances[to] =+ value;            
            

            // addjust the permision, after part of 
            // permited to spend value was used
            allowed[from][msg.sender] -= value;
            
            // rise the Transfer event
            Transfer(from, to, value);
            return true;
        } else { 
            
            return false; 
        }
    }

    

    
    /**
     *
     * balanceOf() - constant function check concrete tokens balance  
     *
     *  @param owner - account owner
     *  
     *  @return the value of balance 
     */                               
    function balanceOf(address owner) constant returns (uint256 balance) {
        return balances[owner];
    }

    
    
    /**
     *
     * approve() - function approves to a person to spend some tokens from 
     *           owner balance. 
     *
     *  @param spender - person whom this right been granted.
     *  @param value   - value to spend.
     * 
     *  @return true in case of succes, otherwise failure
     * 
     */
    function approve(address spender, uint256 value) returns (bool success) {
        
        // now spender can use balance in 
        // ammount of value from owner balance
        allowed[msg.sender][spender] = value;
        
        // rise event about the transaction
        Approval(msg.sender, spender, value);
        
        return true;
    }

    /**
     *
     * allowance() - constant function to check how mouch is 
     *               permited to spend to 3rd person from owner balance
     *
     *  @param owner   - owner of the balance
     *  @param spender - permited to spend from this balance person 
     *  
     *  @return - remaining right to spend 
     * 
     */
    function allowance(address owner, address spender) constant returns (uint256 remaining) {
      return allowed[owner][spender];
    }

}
/*
 * StandardToken - is a smart contract  
 * for managing common functionality of 
 * a token.
 *
 * ERC.20 Token standard: 
 *         https://github.com/eth ereum/EIPs/issues/20
 */
function approve(address spender, uint256 value) returns (bool success) {
        
        // now spender can use balance in 
        // ammount of value from owner balance
        allowed[msg.sender][spender] = value;
        
        // rise event about the transaction
        Approval(msg.sender, spender, value);
        
        return true;
    }
/**
 *
 * approve() - function approves to a person to spend some tokens from 
 *           owner balance. 
 *
 *  @param spender - person whom this right been granted.
 *  @param value   - value to spend.
 * 
 *  @return true in case of succes, otherwise failure
 * 
 */