11. Runtime Environment

• Program runs on the processor.

• Program uses operating system functions and services.

• Program uses one of the memory models:

  • Real mode flat model, 65,536 bytes of addressable memory (ancient MS-DOS .COM files)

  • Real mode segmented model, 1 megabyte (prime-time MS-DOS)

  • Protected mode flat model, modern Windows and Linux:

    • Addressable Memory: 80486 and Pentium - 4 Gigabytes

    • As far as 32-bit Vista is concerned, the world ends at 4,096 megabytes.

    • A 32-bit program can address up to 4 gigabytes of memory.