core of CP/M (BDOS, CCP, core transient commands) did not use any of the Z80-specific instructions, many Z80-based systems used Z80 code in the system-specific BIOS, and many applications were dedicated to Z80-based CP/M machines. Digital Research subsequently partnered with Zilog and American Microsystems to produce Personal CP/M, a ROM-based version of the operating system aimed at lower-cost systems that could potentially be equipped without disk drives. First featured in the Sharp MZ-800, a cassette-based system with optional disk drives, Personal CP/M was described as having been "rewritten to take advantage of the enhanced Z-80 instruction set" as opposed to preserving portability with the 8080. American Microsystems announced a Z80-compatible microprocessor, the S83, featuring 8 KB of in-package ROM for the operating system and BIOS, together with comprehensive logic for interfacing with 64-kilobit dynamic RAM devices. On most machines the bootstrap was a minimal bootloader in ROM combined with some means of minimal bank switching or a means of injecting code on the bus (since the 8080 needs to see boot code at Address 0 for start-up, while CP/M needs RAM there); for others, this bootstrap had to be entered into memory using front-panel controls each time the system was started. CP/M used the 7-bit ASCII set. The other 128 characters made possible by the 8-bit byte were not standardized. For example, one Kaypro used them for Greek characters, and Osborne machines used the 8th bit set to indicate an underlined character. WordStar used the 8th bit as an end-of-word marker. International CP/M systems most commonly used the ISO 646 norm for localized character sets, replacing certain ASCII characters with localized characters rather than adding them beyond the 7-bit boundary. Components In the 8-bit versions, while running, the CP/M operating system loaded into memory had three components: Basic Input/Output System (BIOS), Basic Disk Operating System (BDOS), Console Command Processor (CCP). The BIOS and BDOS were memory-resident, while the CCP was memory-resident unless overwritten by an application, in which case it was automatically reloaded after the application finished running. A number of transient commands for standard utilities were also provided. The transient commands resided in files with the extension .COM on disk. The BIOS directly controlled hardware components other than the CPU and main memory. It contained functions such as character input and output and the reading and writing of disk sectors. The BDOS implemented the CP/M file system and some