Course Content

C Preprocessing

1. Introduction to Preprocessing

Introduction to Compilation Stages Role of the Preprocessor Preprocessing Commands

2. Macros

Symbolic Constant Macro With Arguments Advanced Usage of Symbolic Constant Cancel Macro Stringify Operators

3. Conditional compilation

Fundamentals of Conditional Compilation Pitfalls and Best Practices

Stringify Operators

Stringify operator #

The # operator is used to convert a macro argument into a string literal. This means that if you pass any value to the macro, it will be converted to a string.

Here is an example of usage:

main


              123456789
            
#include <stdio.h>
#define SQR(x) printf("Square " #x " = %d\n", ((x)*(x))) 

int main()
{
   int j = 5;
   SQR(j);
   return 0;
}

The #x operator in the SQR macro is used to turn the x argument into a string. When you pass the j variable to the macro, #x produces the string "j" (i.e. the variable name), not its value.

Thus, in the line

python

#x causes the variable name to be included in the output, and x passes its value (in this case, 5).

If you use a number as an argument, #x will turn the number into a string and then treat it as a number:

main


              12345678910
            
#include <stdio.h>
#define SQR(x) printf("Square " #x " = %d\n", ((x)*(x))) 

int main()
{
   int j = 5;
   SQR(j);
   SQR (54); // number as argument
   return 0;
}

Token Pasting operator ##

The ## operation combines two tokens into one.

main


              12345678
            
#include <stdio.h>
#define CONCAT(x, y) x##y

int main() {
    int myVariable = 10;                   // variable named `myVariable`
    printf("%d\n", CONCAT(my, Variable));  // Result: 10
    return 0;
}

The CONCAT(x, y) macro concatenates the tokens my and Variable, which results in the name myVariable - just like a variable name.

When you call CONCAT(x, y), the preprocessor replaces it with myVariable, and you can access the value of myVariable.

Task

Swipe to start coding

Complete the CREATE_VAR macro, which will concatenate the tokens token1 and token2;
Use the created macro to create the variable "myVariable";
Specify the name of the variable whose contents you want to display on the screen.

Solution

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 5

Stringify Operators

Stringify operator #

The # operator is used to convert a macro argument into a string literal. This means that if you pass any value to the macro, it will be converted to a string.

Here is an example of usage:

main


              123456789
            
#include <stdio.h>
#define SQR(x) printf("Square " #x " = %d\n", ((x)*(x))) 

int main()
{
   int j = 5;
   SQR(j);
   return 0;
}

The #x operator in the SQR macro is used to turn the x argument into a string. When you pass the j variable to the macro, #x produces the string "j" (i.e. the variable name), not its value.

Thus, in the line

python

#x causes the variable name to be included in the output, and x passes its value (in this case, 5).

If you use a number as an argument, #x will turn the number into a string and then treat it as a number:

main


              12345678910
            
#include <stdio.h>
#define SQR(x) printf("Square " #x " = %d\n", ((x)*(x))) 

int main()
{
   int j = 5;
   SQR(j);
   SQR (54); // number as argument
   return 0;
}

Token Pasting operator ##

The ## operation combines two tokens into one.

main


              12345678
            
#include <stdio.h>
#define CONCAT(x, y) x##y

int main() {
    int myVariable = 10;                   // variable named `myVariable`
    printf("%d\n", CONCAT(my, Variable));  // Result: 10
    return 0;
}

The CONCAT(x, y) macro concatenates the tokens my and Variable, which results in the name myVariable - just like a variable name.

When you call CONCAT(x, y), the preprocessor replaces it with myVariable, and you can access the value of myVariable.

Task

Swipe to start coding

Complete the CREATE_VAR macro, which will concatenate the tokens token1 and token2;
Use the created macro to create the variable "myVariable";
Specify the name of the variable whose contents you want to display on the screen.

Solution

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 5

Switch to desktop for real-world practiceContinue from where you are using one of the options below