IBM CGA

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CGA was introduced with the IBM PC (model 5150) in 1981 as an optional upgrade over the MDA display adapter. The supported graphics modes are 320x200 in 4 colors (commonly used by DOS games back then) and 640x200 monochrome, the latter being used by Windows 1.0. Any third party card that claims it's IBM CGA-compatible should support these two modes. CGA cards required a Personal Computer Color Display (model 5153) and will not work with the Personal Computer Display (model 5151), designed for MDA cards. Most "Multisync" monitors should also work.

Windows shipped with a CGA driver early on, probably from the very beggining. The driver was named IBMCOLOR.DIN in Development Release 5 (with IBMCOLOR.CIN alongside it for cursor routines), IBMCOLOR.EXE in the Alpha (with IBMCOLOR.GRB grabber file), CGA.EXE in the Beta and Premiere Edition (with CGA.GRB grabber and CGA.LGO logo file), and finally CGA.DRV since the final 1.01 release. In the display selection screen of Windows 1.0 setup, IBM CGA is usually the very first option named "IBM (or compatible) Color/Graphics Adapter or COMPAQ Personal Computer". It may be renamed to something similar in some OEM releases (e.g. by Zenith).

As mentioned above, this driver uses the high-resolution monochrome mode. It's clear Microsoft chose higher resolution over color for better usability, which is why Windows 1.0 was initially not meant to support color graphics on the PC. Most emulators support at least a basic IBM CGA implementation and Windows 1.0 should work fine in CGA mode on them (subject to emulator specifics of course).