Sunday, December 23, 2012
Preprocessor
Labels:
C Programming
Before compiling a C file, a process called preprocessing is done on the source code by a program called preprocessor.
Consider the C code below:
#include <stdio.h>
void main()
{
printf("Hello World");
}
In the above program the program starts with the line #include <stdio.h>. This line is a preprocessor directive. The preprocessor processes the program before the compiler. All lines beginning with # symbol will be processed by the preprocessor. The #include directive causes the preprocessor to effectively insert the stdio.h file into the C program. When the compiler compiles the program it will see the contents of the stdio.h file instead of the preprocessor directive.
Note: The stdio.h file does not contain the actual statement of the printf function. It only has the information that the function printf exists and can accept a character string.
Consider the C code below:
#include <stdio.h>
void main()
{
printf("Hello World");
}
In the above program the program starts with the line #include <stdio.h>. This line is a preprocessor directive. The preprocessor processes the program before the compiler. All lines beginning with # symbol will be processed by the preprocessor. The #include directive causes the preprocessor to effectively insert the stdio.h file into the C program. When the compiler compiles the program it will see the contents of the stdio.h file instead of the preprocessor directive.
Note: The stdio.h file does not contain the actual statement of the printf function. It only has the information that the function printf exists and can accept a character string.
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment