High Level Assembler runs under the operating systems listed below. Unless otherwise stated, the assembler also operates under subsequent versions, releases, and modification levels of these systems:

• Linux on zSeries (with 32-bit compatibility environment)
• Linux on S/390

High Level Assembler supports the operation codes available with the following mode processors:

• System/370 Architecture
• Extended Architecture (370-XA)
• Enterprise Systems Architecture/370 (ESA/370)
• Enterprise Systems Architecture/390 (ESA/390)
• z/Architecture