C++ Part 42

Review Part V
Local Variables
Variables that are declared within the body of a function definition are
said to be local to that function or to have that function as their scope.
Variables that are declared within the main part of the program are said to
be local to the main part of the program or to have the main part of the
program as their scope. When we say that a variable is a local variable
without any mention of a function and without any mention of the main
part of the program, we mean that the variable is local to some function
definition. If a variable is local to a function, then you can have another
variable with the same name that is declared in the main part of the
program or in another function definition, and these will be two different
variables, even though they have the same name.

---

Overloading a Function Name
If you have two or more function definitions for the same function name,
that is called overloading. When you overload a function name, the
function definitions must have different numbers of formal parameters or
some formal parameters of different types. When there is a function call,
the compiler uses the function definition whose number of formal
parameters and types of formal parameters match the arguments in the
function call.

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Call-by-Reference
To make a formal parameter a call-by-reference parameter, append the
ampersand sign & to its type name. The corresponding argument in a call
to the function should then be a variable, not a constant or other
expression.
When the function is called, the corresponding variable argument
(not its value) will be substituted for the formal parameter. Any
change made to the formal parameter in the function body will be made
to the argument variable when the function is called. The exact details of
the substitution mechanisms are given in the text of this chapter.
EXAMPLE
(OF CALL-BY-REFERENCE PARAMETERS IN A FUNCTION
DECLARATION):
void get_data(int& first_in, double& second_in);

---

Both void functions and functions that return a value can have return
statements. In the case of a function that returns a value, the return statement
specifies the value returned. In the case of a void function, the return
statement simply ends the function call.

C++ Part 34

The call by reference method of passing arguments to a function copies the reference of an argument into the formal parameter. Inside the function, the reference is used to access the actual argument used in the call. This means that changes made to the parameter affect the passed argument.
To pass the value by reference, argument reference is passed to the functions just like any other value. So accordingly you need to declare the function parameters as reference types as in the following function swap(), which exchanges the values of the two integer variables pointed to by its arguments.

// function definition to swap the values.
void swap(int &x, int &y) {
   int temp;
   temp = x; /* save the value at address x */
   x = y;    /* put y into x */
   y = temp; /* put x into y */
  
   return;
}

For now, let us call the function swap() by passing values by reference as in the following example:

#include <iostream>
using namespace std;

// function declaration
void swap(int &x, int &y);

int main () {
   // local variable declaration:
   int a = 100;
   int b = 200;
 
   cout << "Before swap, value of a :" << a << endl;
   cout << "Before swap, value of b :" << b << endl;

   /* calling a function to swap the values using variable reference.*/
   swap(a, b);

   cout << "After swap, value of a :" << a << endl;
   cout << "After swap, value of b :" << b << endl;
 
   return 0;
}

When the above code is put together in a file, compiled and executed, it produces the following result:

Before swap, value of a :100
Before swap, value of b :200
After swap, value of a :200
After swap, value of b :100

C++ Part 33

ASCII - Binary Character Table

Letter	ASCII Code	Binary	Letter	ASCII Code	Binary
a	097	01100001	A	065	01000001
b	098	01100010	B	066	01000010
c	099	01100011	C	067	01000011
d	100	01100100	D	068	01000100
e	101	01100101	E	069	01000101
f	102	01100110	F	070	01000110
g	103	01100111	G	071	01000111
h	104	01101000	H	072	01001000
i	105	01101001	I	073	01001001
j	106	01101010	J	074	01001010
k	107	01101011	K	075	01001011
l	108	01101100	L	076	01001100
m	109	01101101	M	077	01001101
n	110	01101110	N	078	01001110
o	111	01101111	O	079	01001111
p	112	01110000	P	080	01010000
q	113	01110001	Q	081	01010001
r	114	01110010	R	082	01010010
s	115	01110011	S	083	01010011
t	116	01110100	T	084	01010100
u	117	01110101	U	085	01010101
v	118	01110110	V	086	01010110
w	119	01110111	W	087	01010111
x	120	01111000	X	088	01011000
y	121	01111001	Y	089	01011001
z	122	01111010	Z	090	01011010