(Hierarchical File System)along with the Mac's first hard drive, the Hard Disk 20. Finder 5.x displayed drive capacity in binary K units. The Hard Disk 20 Manual specified the HDD as having "Data capacity (formatted): 20,769,280 bytes Bytes per block: 532 (512 user data, 20 system data) Total disk blocks: 39,040 and has the following definition in its glossary:megabyteApproximately one million bytes (1,048,567) of information. A 20 megabyte hard disk holds 20 million bytes of information, or 20,000 kilobytes (20,000K) (Apple Hard Disk 20 Manual)The user data is 39,040 × 512 = 19,988,480 bytes here. 1986 Apple IIgs introduced September 1986 ProDos16 uses MB in a binary sense. Similar usage in "ProDOS Technical Reference Manual" (c) 1985, p. 5 & p. 163 Digital Large System Mass Storage Handbook (c) dated September 1986 "GByte: An abbreviation for one billion (one thousand million) bytes." p. 442 "M: An abbreviation for one million. Typically combined with a unit of measure, such as bytes (MBytes), or Hertz (MHz)." p. 444 1987 Seagate Universal Installation Handbook ST125 listed as 21 "Megabytes" formatted capacity, later document seems to confirm that this is decimal Disk/Trend Report – Rigid Disk Drives, October 1987 First use of GB in a decimal sense in this HDD marketing survey; Figure 1 states "FIXED DISK DRIVES more than 1 GB" market size as $10,786.6 million. Webster's Ninth New Collegiate Dictionary (1987) has binary definitions for kilobyte and megabyte. kilobyte n [from the fact that 1024 (210) is the power of 2 closest to 1000] (1970): 1024 bytes megabyte n (1970): 1,048,576 bytes 1988 Imprimis Wren VII 5 Inch Rigid Disk Drive Data Sheet, printed 11/88 "Capacity of 1.2 gigabyte (GB)" 1989 IBM Enterprise Systems Architecture/370, Reference Summary (GX20-0406-0), p. 50 (the last page), has a two table, one to recap the decimal value of power of 2 and 16 to 260, and one that read: Electronic News, 25 September 1989, "Market 1.5GB Drives" "Imprimis and Maxtor are the only two drive makers to offer the new generation of drives in the 1.5GB capacity range..." "IBM, Hewlett-Packard, Fujitsu, Toshiba, Hitachi and Micropolis are expected to enter the market for 1.5GB capacity..." 1990s 1990 Matsuda et al. refer to 1024 bits (32x32 optoelectronic switches) as "1-kb memory". GEOS ad "512K of memory" The enhanced DOS command line processor 4DOS 3.00 supports a number of additional conditions (DISKFREE, DOSMEM/DOSFREE, EMS, EXTENDED, FILESIZE and XMS) in