360 Assembly/360 Family

There are a number of different computers that used the 360 machine architecture. These include

• IBM 360 series, the Univac 90/60 and 90/70 series, the RCA Spectra 70 series and the English Electric System 4 series
• The IBM 370 and Fujitsu B2000 are, and Univac 90/80 were an enhanced version of the 360 series.
• Smaller versions of the IBM 370 were also released as the 43xx series.
• Larger versions of the 370 were released as the 30xx series.
• An intermediate upgrade to the 370 was released as ESA/390.
• The z/System is similar to the 370/390 series except that the z/System is a 64-bit machine while the IBM 370 and predecessors are 32-bit machines.

In software emulation there are some proprietary applications and two open source ones:

• The Z390 portable assembler provides an Assembler-H (high level) equivalent assembler, Cobol compiler, linkage editor and execution environment for programs written in assembler or Cobol
• The Hercules system provides an emulation of either System 370 or z/System hardware satisfactorily enough to run IBM-based operating systems and user programs running within those systems.

The 360 architecture is a big endian machine (as opposed to the typical Intel or AMD x86 processor, which is little endian), in that values are stored high to low. For example, the 16-bit value 256 would be stored (in hex) as 0100 on a 360-series machine, but be stored as 0001 on an Intel Pentium. The number 1, on the other hand, if rendered as a 16-bit number, would be stored (in hex) as 0001 on a 360, and 0100 on a Pentium. Also, the standard character set on the 360/370/Z-System is EBCDIC, while the Pentium uses ASCII. This can cause a number of headaches in conversion of binary data files from one machine to another.