* Aliens ( Kaypro video game ), a text-only clone of Space Invaders written for the CP / M operating system

Note that the 64x16 TRS-80 mode screen uses only a small part of the monitor screen, because the letters are the same size as the 80 × 25 CP / M screen, this was one of the things that was soon after fixed with the redesign to a commercial product

The Aster computer could use the software written for the popular Tandy TRS-80 computer while fixing many of the problems of that computer, but it could also run CP / M software, with a big amount of free memory ( Transient Program Area, TPA ) and a full 80 × 25 display, and it could be used as a Videotext terminal.

When the boot loader detected a CP / M floppy, the Aster would reconfigure its internal memory architecture on the fly to optimally support CP / M with 60 KB free RAM for programs ( TPA ) and an 80 x 25 display.

With a special configuration tool, the CT-80 could reconfigure its floppy drivers to read and write the floppies of about 80 other CP / M systems.

Also the more interesting software offered for CP / M systems could not run well on a TRS-80.

So they decided to designed a TRS-80 and CP / M software compatible computer system, which ( following the lead of Apple Computer ) they decided to name after a " typical Dutch flower ".

So they called it the Aster CT-80 ( CP / M / Tandy-1980 ).

Because the original designer had left the company another employee completely redesigned most of the system, ( adding a display snow remover circuit, true 80 / 64 column text mode support, ( with different size letters for TRS-80 and CP / M mode, so that in TRS-80 mode the full screen was also used, not just a 64x16 portion of the 80x25 screen ) with an improved font set ( adding " gray scale " version of the TRS-80 mozaik graphics and many special PETSCII like characters ), and a more flexible and reliable floppy disk controller and keyboard interface plus many other small improvements ), also an enclosure was developed for the main computer system, ( in the form of a 19-inch rack for the Eurocards ) and for two floppy disk drives and the power supply.

A software engineer was hired to write the special " dual boot mode " BIOS and the special CP / M BIOS.

The " dual boot mode " BIOS actually discovered whether a TRS-DOS, or Aster CP / M disk was placed in the drive, and would, depending on the type of disk, reorganise the internal memory architecture of the system, to either be 100 % TRS-80 compatible or optimally support CP / M, with as much " workspace " as possible, and the 80x25 video mode.

After the Aster having been a few years on the Market Tandy released its own improved model, the TRS-80 Model 3 computer which solved many of the same problems that the Aster also had solved, but the model 3 still did not fully support CP / M as the Aster did.

The color memory was also available in the " normal " TRS-80 and CP / M text modes, which meant that existing TRS-80 and CP / M software could be easily modified to add color.

On the software front, work was being done to implement the replacement for the aging " user interface " of CP / M, ( the Command Console Processor CCP ) with the more modern ZCPR.

The comparatively low price for a complete computer system with dedicated monitor, its high resolution monochrome text and graphic capabilities and the possibility to run CP / M software also rendered the system attractive for business users, which was reflected by a wide selection of application software.

The first BBSes used homebrew software, quite often written or customized by the SysOps themselves, running on early S-100 microcomputer systems such as the Altair, IMSAI and Cromemco under the CP / M operating system.

Three Danish citizens, Niels Jensen, Ole Henriksen, and Mogens Glad, founded Borland Ltd. in August 1981 to develop products like Word Index for the CP / M operating system using an off-the-shelf company.

The name originated from the Basic Input Output System used in the CP / M operating system ( released in 1976 ), where the BIOS was loaded from disk, with only a small boot loader program stored in read-only memory.

The term BIOS ( Basic Input / Output System ) was invented by Gary Kildall and first appeared in the CP / M operating system in 1975, describing the machine-specific part of CP / M loaded during boot time that interfaces directly with the hardware ( a CP / M machine usually has only a simple boot loader in its ROM ).

* CP / M, " Control Program / Monitor " microcomputer operating system ; a precursor to IBM PC-compatible disk operating systems

Other MFM formats were possible if their characteristics were added to the CP / M C128-specific source code ( available from Commodore ) and the CP / M operating system were re-assembled.

In microcomputers, SWTPC's 6800 and 6809 machines used TSC's FLEX disk operating system, Radio Shack's TRS-80 machines used TRS-DOS, their Color Computer used OS-9, and most of the Intel 8080 based machines from IMSAI, MITS ( makers of the legendary Altair 8800 ), Cromemco, North Star, etc., used the CP / M-80 disk operating system.

Gary Arlen Kildall ( May 19, 1942 – July 11, 1994 ) was an American computer scientist and microcomputer entrepreneur who created the CP / M operating system and founded Digital Research, Inc. ( DRI ).

After hardware manufacturers talked about creating a rival operating system, Kildall started a rush project to develop CP / M 2.

Sams left Gates with the task of finding a usable operating system, and a few weeks later he proposed using the CP / M clone 86-DOS from Seattle Computer Products ( SCP ).

Note that the ICF and ZAAP are essentially identical to CP, but distinguished for software cost control: they are slightly restricted such they cannot be used to run arbitrary operating systems, and thus do not count in software licensing costs ( which are typically based on the number of CPs ).

In addition to PC-DOS, buyers could choose either CP / M-86 or UCSD p-System as operating systems, as well as some flavors of SysV Unix.

For example CP / M machines used many different floppy disk formats, which meant that one machine could not normally read disks from another CP / M machine, and Kermit was used as part of a process to enable the transfer of applications and data between CP / M machines and other machines with different operating systems.

The development and proliferation of personal computers using the CP / M operating system in the late 1970s, and later DOS-based systems starting in 1981, meant that many sites grew to dozens or even hundreds of computers.

Design features of the PDP-11 influenced the design of microprocessors such as the Motorola 68000 ; design features of its operating systems, as well as other operating systems from Digital Equipment, influenced the design of other operating systems such as CP / M and hence also MS-DOS.

However, booting CP / M was only supported from disks in the standard Commodore GCR format ; the MFM formats could only be used once the system was running.

" In an appendix he called DOS " plain and simple theft " because its first 26 system calls worked the same as CP / M's.

It was named after the amateur radio callsign of Phil Karn, who first wrote the software for a CP / M system and then ported it to DOS on the IBM PC.

It offered MFM capability for accessing CP / M disks, improved speed, and somewhat quieter operation, but was only manufactured until Commodore got its production lines going with the double-sided 1571.

By 1981, at the peak of its popularity, CP / M ran on 3, 000 different computer models and DRI had $ 5. 4 million in yearly revenues.

* The CPRR named one of its steam locomotives ( CP No. 4 ) after him.

UCSD p-System ( Version IV, supplied by SofTech ) was one of three operating systems ( along with PC-DOS and CP / M-86 ) that IBM offered for its original IBM PC ; but the p-System never sold very well for the IBM PC, mainly because of a lack of applications and because it was more expensive than the other choices.

The concept of drive letters, as used today, presumably owes its origins to IBM's VM family of operating systems, dating back to CP / CMS in 1967 ( and its research predecessor CP-40 ), by way of CP / M.

* The drive letter syntax chosen for CP / M was inherited by Microsoft for its operating system MS-DOS and later, OS / 2 and the Microsoft Windows family.

This was done both to reduce costs, and because access to CP memory required 10 PP clock cycles: when a PP accesses CP memory, the data is available next time the PP receives its slot time.

Digital Research fought a long losing battle to promote CP / M-86 and its multi-tasking multi-user successor Concurrent CP / M-86, and eventually decided that they could not beat the Microsoft-IBM lead in application software availability, so they modified Concurrent CP / M-86 to allow it to run the same applications as MS-DOS and PC DOS.