added C

C/call_by_reference.c

@@ -0,0 +1,18 @@
+// Call by reference example
+
+#include <stdio.h>
+
+void mathoperations(int x, int y, int *s, int *d);
+void main()
+{
+    int x=20, y=10, s, d;  // x and y input arguments, s and d output arguments
+    mathoperations(x, y, &s, &d);
+    printf("  s=%d\n  d=%d\n", s,d);
+}
+
+
+void mathoperations(int a, int b, int *sum, int *diff)  // x to a, y to b, address of s to sum and address of d to diff
+{
+    *sum=a+b;   //sum and diff are pointer variables
+    *diff=a-b;  //*sum and *diff are pointers
+}

C/function.c

@@ -0,0 +1,19 @@
+//Function example
+
+#include <stdio.h>
+
+int sum(int a, int b); // function declaration or prototype
+void main()
+{
+    int num1=10,num2=20,result;
+    result=sum(num1,num2);  //function call
+    printf("Sum of numbers is: %d",result);
+
+}
+
+int sum(int a, int b) // Function header
+{
+int s;
+s=a+b;
+return s;
+}