CADO Systems
| Company type | Private |
|---|---|
| Industry | Computer hardware, Software development |
| Founded | 1976 |
| Fate | Acquired by Contel Business Systems in 1983; merged with NDS in 1989 to form VERSYSS |
| Headquarters | Torrance, California , United States |
| Products | Minicomputers, CADOL programming language, CAT series computers, Tiger product line |
CADO Systems was established in 1976 in Torrance, California, by ex-employees of Microdata Corporation, specializing in minicomputers and software development. The firm maintained a manufacturing facility and a software engineering division located in Cork, Ireland. In 1983, Contel Business Systems acquired CADO, which later merged with NDS in 1989, forming the company known as VERSYSS.
Business model
Both CADO and Contel focused on delivering customized computing solutions and operating systems tailored for specific vertical markets. Their offerings facilitated swift implementation of industry-focused applications within small business sectors including finance (covering General Ledger and Accounts Payable/Receivable), wholesale distribution (Inventory management and Point of Sale), travel (Ticketing and Passenger Management), and healthcare billing.
CADO was among the first to develop Intel microcomputer-based business platforms integrating disk storage, application software, and a unique interpreted language resembling BASIC called "CADOL." Initial development prototypes utilized the Intel 8008 processor in 1973; by 1975, systems based on the Intel 8080 were commercially available. Early versions supported single-user access through serial terminals, progressing to multitasking /4 models accommodating up to four users via Intel 8085 CPUs coupled with proprietary memory-switching technology. The /8 variant combined two /4 units to serve eight users sharing a common hard disk.
The CAT series (CAT I, II, III) introduced integrated CRT displays with built-in disk drives by 1981. The CAT III model allowed three users to connect via serial terminals to a system console housing the central processing unit and storage devices. Production exceeded 25,000 CAT units alongside 200,000 terminals. These terminals featured custom firmware enabling protected input fields.
CADO’s CADOL interpreter was embedded in EPROMs for immediate execution at startup. Subsequent improvements increased program overlay capacity from 256 bytes up to 65 KB, enhancing application sophistication and enabling transparent code loading. The compiler was rewritten using Intel 8085 assembly language to boost performance.
Although the software team favored Motorola 68000 processors, hardware Vice President Bob Thorne prioritized Intel’s extensive chipset offerings—including serial interfaces, DMA controllers, and interrupt handling—aligning with the emerging x86 industry standards. Development efforts included two disk controller designs that remained incomplete.
The Tiger product line represented CADO’s transition to 16-bit Intel 8086-based systems featuring a Multibus backplane architecture that supported various plug-in cards: CPU modules running CADOL III, terminal interface cards with multiple serial ports, and optional disk processors based on the Intel 8089. This modular architecture allowed scalable multi-user systems resembling mainframe capabilities.
By the mid-1980s, CADO incorporated UUCP-based Usenet and email connectivity and deployed UNIX servers internally to manage network services. However, founder George Ryan departed prior to the IBM PC launch—a pivotal event that significantly influenced CADO’s market standing. Following this period, CADO was absorbed into Contel.
Contel’s Tiger ATS series (models Tiger 8/16/32/64) expanded user support from eight up to sixty-four simultaneous users utilizing multiple 8086/8089 processors. Chassis sizes varied from compact units to larger configurations comparable in size to household refrigerators.
In 1989, VERSYSS introduced the VS/1 product family (models 150/250/500), marking a shift from proprietary hardware platforms toward commodity components running an AT&T SYSVR3 Unix derivative. Backward compatibility with legacy MMOS applications was preserved through specialized proprietary boards installed on the system bus, ensuring seamless user operation.
By 1993, VERSYSS collaborated with IBM to port MMOS onto IBM RS/6000 systems, eliminating most proprietary hardware elements except for terminal firmware.
Louis Thompson currently holds the original archives documenting CADO’s systems and operational history.
Other Products
In 1985, Contel introduced the CADOS emulator, designed to enable CADO software operation on conventional IBM PC systems, thereby broadening its range of computer emulation and compatibility products.