Stop a contract from executing

Stop a Contract from Executing

function transfer(address _to, uint256 _value) {
        /* Check if sender has balance and for overflows */
        require(balanceOf[msg.sender] >= _value && balanceOf[_to] + _value >= balanceOf[_to]);

        /* Add and subtract new balances */
        balanceOf[msg.sender] -= _value;
        balanceOf[_to] += _value;
    }