Macros in C Programming – Don’t Consider it as an Outdated Feature

Today, macros in C is considered as outdated in modern programming practices, it still finds applications in C by making things easier for the programmer. We will help you to develop a clear understanding of macros by covering even the minute concepts.

In this tutorial, we will discuss:

• Macros in C Programming
• Types of macros
• Different predefined macros

1. Macros in C Programming

Macros are nothing but a piece of code based on the #define preprocessor. In the C programming language, a macro would generally look like:

#define MACRO macro_value

Key takeaway: It is important to note that the macros are not terminated by a semicolon (;)

For a better understanding of Macros, it is important to understand preprocessors in C.

2. Types of Macros in C Programming

In C, Macros are broadly classified into two distinct types. They are namely:

2.1 Object-like Macros

It appears to be a symbolic constant. It can be termed as an alternative way to define an identifier used to represent constant expressions. The simplest example would be:

#define PI 3.14

2.2 Function-like Macros

It is an expression, used to perform a particular operation. It is an alternative way to define a function. A simple example would be:

#define RECTANGLE(l,b) l*b

Here is a code in C that illustrates the use of macros to find the area of a rectangle:

#include<stdio.h>
#define RECTANGLE(l,b)l*b
int main()
{

printf("Welcome to DataFlair tutorials!\n\n");

int length = 3, breadth = 4;
int area = RECTANGLE(length,breadth);
printf("The area is: %d\n", area);
return 0;
}

Having problems in understanding the above program? Check this out Basic Syntax Rules – Learn the ABC’s of  CProgramming

Code on Screen-

Output-

Types of Predefined Macros in C

Here is a table that summarizes some of the basic macros used in the C programming language:

1. _DATE_  – Used to represent the current date in MM DD YYYY format.
2. _STDC_  – Used to indicate when the compiler compiles the code successfully by returning the value 1.
3. _TIME_  – Represent the current time in HH:MM:SS.
4. _LINE_  – Represent the current line number.
5. _FILE_  – Represent the current file name.

Here is a code in C that illustrates the use of macros:

#include<stdio.h>
int main()
{

printf("Welcome to DatafLair tutorials!\n\n");

printf("The current date is: %s\n", __DATE__ );
printf("The current time is: %s\n", __TIME__ );
printf("The total lines in the code is: %d\n", __LINE__ );
printf("The file name is: %s\n", __FILE__ );
printf("STDC would return the value: %d\n", __STDC__ ); // %d is used since it would return an integer value
return 0;
}

Code on Screen-

Output-

Quiz on Macros in C

Summary

In this tutorial, we discussed the basic meaning of macros, its 2 basic types with appropriate examples. We further carried our discussion on the various types of predefined macros available in the C programming with the help of a program.

It’s the right time to explore Typecasting and Type Conversion in C

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