Yes, they are completely different from a coding standpoint.
The PRIMARY differences are in the hardware capabilities - Phones have a RISC or ARM cpu, which means much less commands available,much less on-chip cache memory, and much less power requirements. So a 1.2Ghz ARM or RISC chip is HUGELY different from an Intel or AMD 1.2Ghz chip in a laptop or desktop.
From there the next logical stop is in the amount of storage space available to each device- which affects swapspace for processing, space to store large, small, & drivers & actual OS software, meaning that You're limited to between 4Gbs for older phones & 32Gbs for newer phones to do EVERYTHING that makes the phone a non-brick. While computers can have up to 4 Terabytes internally,& most laptops about 1 terabyte.
Then We get to the video hardware - a phone only has to run a 6 inch screen area, while a computer can run a 55" plus display monitor or TV set in full 4k definition. This OBVIOUSLY takes a lot more hardware, RAM, and heat & electricity than a phone's simple chip with maybe 16 Megabytes of graphics RAM.
Those are just the starting points... There are many more to be looked up.