About short circuit in power supplies
The constant current and constant voltage modes are actually voltage set and current limited modes. if you set it to 5V and 1A, then the power supply will operate such that the voltage is held at 5V as long as the current is less than 1A, but will reduce the voltage if the current exceeds 1A.

Imagine you connect a variable resistor to the output of such a supply, and keep the resistance at 1k. The power supply has a voltage of 5V across it, and draws a current of 5mA - well within the current limit, so the current limit controller does nothing. Now you slowly reduce your variable resistance, and watch the current rise - as long as current &lt;1A the current limiter does nothing.

Say you reach 5.0 Ohms, and the current has just climbed to 1A.
Now if you decrease the resistance a little further, the current will  increase a little beyond 1A, and the current controller will start to reduce the voltage till the current comes back to 1A. So if you reduce R to 4.95ohms, the current will rise to 5V/4.95 Ohms=1.01A, at which point the current control will keep decreasing the voltage till current reaches 1A. This voltage will be 4.95V.

If you dead short the output, the output current will remain 1A, and the voltage will be 1A times the resistance of the shorting wire.