3. Small, Medium, Compact, Large, and Huge Models

• The traditional memory models recognized by many languages are small, medium, compact, large, and huge.

  • Small model supports one data segment and one code segment.

    • All data and code are near by default.

  • Large model supports multiple code and multiple data segments.

    • All data and code are far by default.

  • Medium and compact models are in-between.

  • Medium model supports multiple code and single data segments

  • Compact model supports multiple data segments and a single code segment.

  • Huge model implies that individual data items are larger than a single segment, but the implementation of huge data items must be coded by the programmer.

  • Tiny-model programs run only under MS-DOS. Tiny model places all data and code in a single segment. Therefore, the total program file size can occupy no more than 64K.

    • Since the assembler provides no direct support for this feature, huge model is essentially the same as large model.

• In each of the models, you can override the default. For example, you can make large data items far in small model, or internal procedures near in large model.