Tag: execution speed

In today’s video tutorial lets see the difference between a Macro with argument and a simple function.

Related Read:
Macros With Arguments: C Program
Function / Methods In C Programming Language

Video Tutorial: Macro With Argument v/s Function Call: C Program

Source Code: Macro With Argument v/s Function Call: C Program

#include<stdio.h>

#define PI 3.14159265358979323846
#define AREA(r) ( PI * r * r )

double circle_area(float);

int main()
{
    float r;

    printf("Enter radius of Circle\n");
    scanf("%f", &r);

    printf("Area of Circle, using Macro is %f\n", AREA(r));
    printf("Area of Circle, using Function is %f\n", circle_area(r));

    return 0;
}

double circle_area(float r)
{
    return( 3.14159265358979323846 * r * r );
}

Output:
Enter radius of Circle
5
Area of Circle, using Macro is 78.539816
Area of Circle, using Function is 78.539816

As you can see in above output the result is same for Macro and function call. Now the question is, when to use macros and when to use functions?

When to use macros and when to use functions?

Macro: If a macro template is used 100 times inside a C program, all these macro template will be replaced with its macro expansion before its passed to the compiler. This process is called as preprocessing, and it’s done by preprocessor. Because of this, the size of the program increases.

Function: Function definition is written only once and even if its called 100 times inside a program it won’t increase the program size. Whenever there is a function call, the control is passed to the function definition where some logical operation is performed and then a meaningful result is returned back to the calling function. This takes some time.

So the trade off is between memory space and time.

If memory is not an issue, then you can simply use Macros – as it brings in speed of execution as an advantage. But if memory space is an issue – if you’re writing for a mobile device, then it’s better to go with functions. Though its slower, it uses less memory space.

While coding for bigger real-time projects you’ll surely need the knowledge of macros and macros with argument, so know the syntax and it’s advantages. In this fast moving world speed of execution really matters. And C programming specifically is famous and used often for its speed and its easy integration(and interaction) with the hardware devices.

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