# Invoking armcc

The general form of the command for invoking the ARM C compiler is:

``

    armcc

By default, the C compiler looks for source files, and creates object, assembler and listing files, in the current directory.

Many aspects of the compiler's operation can be controlled via command-line options. All options are prefixed by a minus sign.

There are two classes of option: keywords and flags. Keywords are recognised in upper case or lower case. A flag is a single letter, the case of which is sometimes important to the ARM C compiler.

Because some systems (such as Unix) are very case sensitive, the case of flags is most important when you are building portable makefiles. By using the conventions common to many C compilers, you can move a makefile between different environments at minimum cost.