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12 digi.com Introduction to Dynamic C
2.2 Dynamic C Enhancements and Differences
Dynamic C differs from a traditional C programming system running on a PC or under UNIX. The reason?
To better help customers write the most reliable embedded control software possible. It is not possible to
use standard C in an embedded environment without making adaptations. Standard C makes many
assumptions that do not apply to embedded systems. For example, standard C implicitly assumes that an
operating system is present and that a program starts with a clean slate, whereas embedded systems may
have battery-backed memory and may retain data through power cycles. Rabbit has extended the C lan-
guage in a number of areas.
2.2.1 Dynamic C Enhancements
Many enhancements have been added to Dynamic C. Some of these are listed below.
• Function Chaining, a concept unique to Dynamic C, allows special segments of code to be embedded
within one or more functions. When a named function chain executes, all the segments belonging to
that chain execute. Function chains allow software to perform initialization, data recovery, or other
kinds of tasks on request.
• Costatements allow cooperative, parallel processes to be simulated in a single program.
• Cofunctions allow cooperative processes to be simulated in a single program.
• Slice Statements allow preemptive processes in a single program.
• Dynamic C supports embedded assembly code and stand-alone assembly code.
• Dynamic C has keywords that help protect data shared between different contexts (shared) or stored in
battery-backed memory (protected).
• Dynamic C has a set of features that allow the programmer to make the fullest use of xmem (extended
memory). The compiler supports a 1 MB physical address space.
Normally, Dynamic C takes care of memory management, but there are instances where the program-
mer will want to take control of it. Dynamic C has keywords and directives to help put code in the
proper place, such as: root, xmem, and #memmap.
See Chapter 9 for further details on memory management.