Explain what a call stack is in the context of program execution.

Call stack is a data structure used during program execution to store information about function calls.

When a function is called, a record (frame) is placed on the stack, containing:

• Return address (where to return after the function completes)
• Local variables of the function
• Function parameters

After the function finishes, this frame is removed from the stack, and control returns to the call site.

In Go, the call stack helps track the sequence of function calls, which is important for error handling, panics, and debugging.

Example:

func a() {
    b()
}
func b() {
    c()
}
func c() {
    // here the call stack: c -> b -> a
}

At the moment of executing c(), the call stack contains information about c, b, and a.