### Theory:

Predecessor and successor of an integer:

Let us first recall the successor and predecessor.
The successor of any number is adding $$1$$ to the given number.

The predecessor of any number is subtracting $$1$$ to the given number
We can easily found predecessor and successor using number line.
1. To find the predecessor of any number, move $$1$$ unit to the left side of that number.

2. To find the successor of any number, move $$1$$ unit to the right side of that number.
Example:
1. Find the predecessor of $$-1$$.

Move $$1$$ unit to the left side of $$-1$$.

The predecessor of $$-1$$ is $$-2$$.

2. Find the predecessor of $$1$$.

Move $$1$$ unit to the left side of $$1$$.

The predecessor of $$1$$ is $$0$$.

3. Find the successor of $$2$$.

Move $$1$$ unit to the right side of $$2$$.

The successor of $$2$$ is $$3$$.

4. Find the successor of $$-5$$.

Move $$1$$ unit to the right side of $$-5$$.

The successor of $$-5$$ is $$-4$$.