Keil Software — Cx51 Compiler User’s Guide 17
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Chapter 1. Introduction
The C programming language is a general-purpose, programming language that
provides code efficiency, elements of structured programming, and a rich set of
operators. C is not a big language and is not designed for any one particular area
of application. Its generality combined with its absence of restrictions, makes C
a convenient and effective programming solution for a wide variety of software
tasks. Many applications can be solved more easily and efficiently with C than
with other more specialized languages.
The Cx51 Optimizing C Compiler is a complete implementation of the American
National Standards Institute (ANSI) standard for the C language. Cx51 is not a
universal C compiler adapted for the 8051 target. It is a ground-up
implementation dedicated to generating extremely fast and compact code for the
8051 microprocessor. Cx51 provides you the flexibility of programming in C
and the code efficiency and speed of assembly language.
The C language on its own is not capable of performing operations (such as input
and output) that would normally require intervention from the operating system.
Instead, these capabilities are provided as part of the standard library. Because
these functions are separate from the language itself, C is especially suited for
producing code that is portable across a wide number of platforms.
Since Cx51 is a cross compiler, some aspects of the C programming language
and standard libraries are altered or enhanced to address the peculiarities of an
embedded target processor. Refer to “Chapter 3. Language Extensions” on page
85 for more detailed information.
Support for all 8051 Variants
The 8051 Family is one of the fastest growing Microcontroller Architectures.
More than 400 device variants from various silicon vendors are today available.
New extended 8051 Devices, like the Philips 80C51MX architecture are
deticated for large application with several Mbytes code and data space.
For optimum support of these different 8051 variants, Keil provides the several
development tools that are listed in the table below. A new output file format
(OMF2) allows direct support of up to 16MB code and data space. The CX51
compiler is a variant of the C51 compiler that is design for the new Philips
80C51MX architecture.
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