This computer is based on an Interact computer (see them in Wikipedia.) It had an 8080 processor with 8Kb of memory. It used a cassette player to read/record programs. While it came with games, it also had 'Microsoft' Basic and a 'Monitor' program to write programs in machine language.
Interact computers folded in 1979. I bought several for pennies on the dollar. After playing with them, I decided to up the ante and turn one of them into a HP9810 'lookalike'!
To do this, I started with a B/W CRT display, a 40 character/line line printer, and better keyboard (the Interact had a 'Chiclets' keyboard). I also added a PCB with a lot more RAM and EPROMs. In the EPROMS, I had Basic, 'Monitor' and a Modem interface. To house all of this, I fabricated an aluminum chassis and housing. I added a 25-pin serial port so that I could attach a phone modem. The CRT & printer required adding interface PCB boards. The cassette player is from the original Interact computer.