Home computer based on the RCA 1802 microprocessor,
The COMX-35 was a home computer that was one of the very few systems to use the RCA 1802 microprocessor, the same microprocessor that is also used in some space probes.
The COMX-35 had a keyboard with an integrated joystick in place of cursor keys. It was relatively inexpensive and came with a large collection of software. COMX-35 was manufactured in Hong Kong by "COMX World Operations Ltd" and was released in the Netherlands, the United Kingdom, Sweden, New Zealand, Australia, Finland, Norway, Italy, Singapore, Turkey and the People's Republic of China.
Hardware.
Memory.
The COMX-35 has 35 KB of RAM. It consists of 32 KB of User RAM of which roughly 30 KB is available for BASIC code, with the rest reserved for use by the BASIC System ROM. The remaining 3 KB of RAM is used by the Video Interface System.
Video interface system.
The COMX-35 uses the RCA CDP1869 and CDP1870 Video Interface System (VIS), consisting of the CDP1869 address and sound generator and the CDP1870 colour video generator.
The COMX-35 automatically detects the Refresh rate. The VIS runs on 5.626 MHz in PAL and 5.67 MHz in NTSC. This frequency is halved and used to clock the CPU. The VIS is also responsible for the timing of the interrupts and non display period. Video memory can only be accessed during the non display period, which allows for execution of 2160 machine cycles in PAL and 1574 cycles in NTSC. To maximize access to the Video memory, the program can be paused until the non display period by checking EF1 in a loop.
The Video memory is divided into 1 KB RAM page memory and 2 KB RAM character memory.
The page memory stores the ASCII code for each character position on the screen. The screen had 960 characters where position 0 (left top corner) could be accessed by memory location [Tag] (before scrolling). The character memory stored the character definition of each ASCII character and can be accessed at memory locations [Email]
Models.
The COMX-35 came in two colours, with either a white or black keyboard. Later models also included a monitor port.
A second model called the COMX PC1 improved the keyboard and added a joystick port. A clone known as the Savla PC1 was sold in India.
Peripherals.
The COMX-35 has one 44-pin external connector for additional expansion options in the form of interface cards. A section of memory is reserved for use by any interface card.
The following hardware was available:
Software.
West Electronics, the company importing the COMX-35 in The Netherlands, provided most of their software for free and without copyrights (or for a small fee for tape, disk and/or shipment). West Electronics also organized different competitions for homebrew software. Homebrew development for the COMX-35 is still active in The Netherlands as a result.
The most popular game on the COMX-35 was 'Worm' (known in The Netherlands as 'Eet een wurm'). This was a very basic adaptation of "Snake". Playing the game long enough would eventually cause it to run out of places to place new food, slowing the game down.
Known bugs.
One can crash the COMX-35 by simply typing 65535 as the line number in BASIC. 
The BASIC interpreter can be put into a hard-lock by pressing the return key while the 'READY' prompt is displayed. This is because the prompt is treated as a 'READ' command, despite the lack of DATA statements in the program.
The '!' symbol in the character set displays a red dot just above the black dot.
Emulator.
Emma 02 is capable of emulating the COMX-35 along with other systems which share a similar chip-set.
References.
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