Z80 Assembler, disassembler and 'Singlestep' debugger.
In 256K mode up to 64Kb of source could be processed, with 512K up to 256Kb of source could be assembled.
The editor could also import 32-column formatted source files from LERM Software's other ZX Spectrum based utilities and offered 976 labels (15Kb storage of 14-byte length).
Other features allowed the merging of source files, a help page/scratchpad temporary storage for notes with the ability to do base conversions, 16-bit to high/low byte splitting and access to the disassembler and singlestep debugger.