A Quick Introduction to C Programming

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Writing and Running Programs

1. Write text of program (source code) using an editor such as emacs, save as file e.g. my_program.c


2. Run the compiler to convert program from source to an “executable” or “binary”:
$ gcc –Wall –g my_program.c –o my_program

3-N. Compiler gives errors and warnings; edit source file, fix it, and re-compile


A Quick Digression About the Compiler

In Preprocessing, source code is “expanded” into a larger form that is simpler for the compiler to understand. Any line that starts with ‘#’ is a line that is interpreted by the Preprocessor.

Include files are “pasted in” (#include)
Macros are “expanded” (#define)
Comments are stripped out ( /* */ , // )
Continued lines are joined ( \ )


The number of a slot is its Address.
One byte Value can be stored in each slot


What is “Memory”?

A Type names a logical meaning to a span of memory. Some simple types are:

a single character (1 slot)
an array of 10 characters
signed 4 byte integer
4 byte floating point
signed 8 byte integer