1. Lab guide # 12
Review C Preprocessor
And Q&A

2. Key points #include Preprocessor Directive
#define Preprocessor Directive: Symbolic Constants
#define Preprocessor Directive: Macros
#error and #pragma Preprocessor Directives
# and ## Operators
Line Numbers
Predefined Symbolic Constants
Assertions

3. For example in “constants.h” we have
#ifndef _CONSTANT_
#define _CONSTANT_
#define pi
#define h e /* Planck's constant/2PI in J-sec */
#define am e /* Electron rest mass in kg */
#define q e /* Electron charge */
#define kb e /* Boltzmann constant J/Kelvin */
#define eps_ e /* Permittivity of free space. unit F/m */
#define max_electron_number
#endif //_CONSTANT_

4. Macro Operation defined in #define
A macro without arguments is treated like a symbolic constant
A macro with arguments has its arguments substituted for replacement text, when the macro is expanded
Performs a text substitution – no data type checking
The macro
#define CIRCLE_AREA( x ) ( PI * ( x ) * ( x ) )
would cause
area = CIRCLE_AREA( 4 );
to become
area = ( * ( 4 ) * ( 4 ) );

5. Assertions assert macro Header <assert.h>
Tests value of an expression
If 0 (false) prints error message and calls abort
Example:
assert( x <= 10 );
If NDEBUG is defined
All subsequent assert statements ignored
#define NDEBUG

6. Review chapter 7-12 for Final Exam
C pointers
C characters and Strings
C formatted Input/Output
C Structures, Unions, Bit manipulations and Enumerations
C File processing
C Data structures

7. Q&A About HW and Lab assignments