On the 74ls74 d flip-flop, the clk input has a small triangle. the pr (preset) and clr (clear) inputs have a circle. what do these symbols mean?

A flip-flop is a device that stores a single binary digit of data.

The small triangle means that the clock signal is an edge-triggered signal, while the circles mean that the signal of the flip-flop is low-active

The shapes used in flip-flops are:

Triangles are used to indicate the trigger of the flip-flop, while circles are used to represent the signal

From the question, we understand that:

The small triangle represents an edge-triggered clock signal, while the circles represent that the signal of the flip-flop is low-active

Read more about flip-flops at:

link

the today function returns a valid value without any arguments.

the today function returns the current date based on the computer's date setting and formatted as a date. today takes no parameters, but requires that you use empty parentheses