Let me define what a piece of code needs to do to be a "kernel": it needs to manage some resources to allow other programs to run using those resources. E.g. memory, cpu time, I/O peripherals etc.
You know a kernel when you see one.
"With the aid of the firmware and device drivers, the kernel provides the most basic level of control over all of the computer's hardware devices. It manages memory access for programs in the RAM, it determines which programs get access to which hardware resources, it sets up or resets the CPU's operating states for optimal operation at all times, and it organizes the data for long-term non-volatile storage with file systems on such media as disks, tapes, flash memory, etc."[1]
A program that prints "hello world" doesn't come close to meeting that description.