The document discusses C programming concepts including function calls by value vs reference, recursive functions, and examples of swapping values using call by value and reference. Functions can be called by passing values or references to parameters. Call by value copies the values while call by reference uses the same memory locations, allowing changes to reflect in the caller. Examples demonstrate swapping values using each method and calculating a factorial using recursion by calling the function within itself.

1. C PROGRAMMING
BY MOHAMMED TAJUDDIN

2. C PROGRAMMING
• Functions can be invoked in two ways: Call by Value or Call by
Reference. These two ways are generally differentiated by the type of
values passed to them as parameters.
• The parameters passed to function are called actual parameters
whereas the parameters received by function are called formal
parameters.

3. C PROGRAMMING
• Call By Value: In this parameter passing method, values of actual
parameters are copied to function’s formal parameters and the two
types of parameters are stored in different memory locations. So any
changes made inside functions are not reflected in actual parameters
of the caller.
• Call by Reference: Both the actual and formal parameters refer to the
same locations, so any changes made inside the function are actually
reflected in actual parameters of the caller.

4. C PROGRAMMING
#include<stdio.h>
void swap(int,int);
void main(){
int a=10,b=20;
swap(a,b);}
printf(“%d%d”,a,b);}
void swap(int x,int y){
int t=x,x=y,y=t;
printf(“%d%d”,x,y);
}

5. C PROGRAMMING
#include<stdio.h>
void swap(int*,int*);
void main(){
int a=10,b=20;
printf(“%d%d”,a,b);
swap(&a,&b);}
void swap(int* x,int* y){
int t=*x,*x=*y,*y=t;
printf(“%d%d”,*x,*y);
}

6. C PROGRAMMING
Recursive function :
Function calling it self is called as recursive function.
Example :
#include<stdio.h>
int fact(int);
void main(){
int n,result;
printf(“enter number”);
scanf(“%d”,&n);
result=fact(n);
printf(“%d”,result);}

7. C PROGAMMING
int fact(int){
int res;
if(n==0){
res=1;}
else{
res=n*fact(n-1);}
return res;
}