8-bit is a computer information measurement that was commonly used to refer to hardware and software at an age when computers could only store and execute 8 bits per data block. This limitation was mostly caused by the CPU technology available at the time, which software had to adhere to. As a result, the images were blocky and the computation times were long.
Because the ALU on the 8085 processor is 8 bits (Arithmetic Logic Review). The ALU on the 8086 processor is also 16 bits.