Given a string A and two integer B and C.Find and return the substring of A starting from index B and ending with index C.

Sure, here is a step by step solution in Python:

1. First, define the function with the required parameters. In Python, we define a function using the def keyword. Let's call our function substring and it will take three parameters: A (the string), B (the starting index), and C (the ending index).

def substring(A, B, C):

2. Next, we need to extract the substring from A starting from index B and ending at index C. In Python, we can do this using slicing. The syntax for slicing in Python is sequence[start:stop], where start is the starting index and stop is the ending index. Note that the character at the stop index is not included in the slice.

    return A[B:C+1]

3. Now, our function is complete. Here is the full code:

def substring(A, B, C):
    return A[B:C+1]

4. You can call this function with a string and the starting and ending indices to get the substring. For example:

print(substring("Hello, World!", 7, 12))  # Output: "World"

This will return the substring of "Hello, World!" starting from index 7 and ending at index 12, which is "World".