Macros vs Functions

Macros are pre-processed which means that all the macros would be processed before your program compiles. However, functions are not preprocessed but compiled.

See the following example of Macro:

#include<stdio.h>
#define NUMBER 10
int main()
{
     printf("%d", NUMBER);
     return 0;
}

Output:
10

See the following example of Function:

#include<stdio.h>
int number()
{
    return 10;
}
int main()
{
    printf("%d", number());
    return 0;
}

Output:
10

In short,

Macro features:

Macro is Preprocessed
No Type Checking
Code Length Increases
Use of macro can lead to side effect
Speed of Execution is Faster
Before Compilation macro name is replaced by macro value
Useful where small code appears many time
Macro does not Check Compile Errors

Function features:

Function is Compiled
Type Checking is Done
Code Length remains Same
No side Effect
Speed of Execution is Slower
During function call, Transfer of Control takes place
Useful where large code appears many time
Function Checks Compile Errors