Texas Instruments TI89 Developer Guide - Page 65

23 5. Flash Applications vs. ASM Programs Resides in Executes in Size Data segment Copy protection O menu User interaction Flash Application ASM Program protected Flash memory - The Flash memory occupied by the OS and applications is protected from inadvertent or malicious changes. RAM or archive Flash memory - ASM programs can be archived but must execute in RAM. protected Flash memory - Flash apps are executed in place, i.e., the app does not need to be moved to RAM before it can be executed. RAM - ASM programs can only be executed in RAM. Calculator hardware does not allow 68000 instructions to execute in archive memory. The OS makes a temporary RAM copy of an archived ASM program before executing it. ≤ 4 MB - Flash apps are limited by the amount of free Flash memory but can be no bigger than 4 MB. ≤ 24 KB - The current version of the heap manager cannot allocate any chunk of memory larger than 64 KB. The lower 24 KB limit is part of the antipiracy mechanism. Yes - The OS allocates a data segment for each application. Applications can define and reference global and static variables any of which may have an initial value. No - ASM programs must allocate variables on the stack or within the code segment. This is not difficult in assembly language but C never allocates static/global variables in the code segment. Yes - A Flash application can only be installed in calculators that have a license for the software. All calculators come with a freeware/shareware key which allow freeware/shareware applications to be installed without an additional license. None - ASM programs can be freely copied between calculators. Yes - Interactive Flash applications appear on the O menu. No - ASM programs are not full-fledged applications. They can only be called from TI-BASIC as subprograms or from the Home screen author line. Event driven - Flash applications participate in cooperative multitasking through the OS. The OS provides default behavior for many of the special keys such as O, 3 and function keys. Polled - ASM programs must poll the keyboard to receive input from the user. No other applications can run until the ASM program returns to the OS. ASM programs do not get any automatic behavior for special keys on the keyboard. TI-89 / TI-92 Plus Developer Guide Not for Distribution Beta Version January 26, 2001