The lecture covers foundational concepts in C++ programming, including the structure of a program, the importance of variables, and the declaration syntax. It emphasizes the need for a text editor and a C++ compiler, explains program tokens, and discusses the initialization of variables to avoid errors. Additionally, examples demonstrate input and output operations along with a homework assignment to complete exercises from chapter 1.

1. COMPUTATIONAL PHYSICS
Lecture 2
Dr.Alliya
Department of Physics
LCWU

2. PROGRAM
• A program is a sequence of instructions that can be executed by a computer.
• C++ (pronounced “see-plus-plus”) is one of the most powerful programming languages available. It gives the
programmer the power to write efficient, structured, object-oriented programs
• you need to have
• text editor - software system that allows you to create and edit text files e.gWordPad and Notepad
• C++ compiler installed on your computer - software system that translates programs into the machine language
• C++ is case-sensitive
//This program simply prints “Hello,World!”:
#include <iostream>
int main()
{
std::cout << "Hello,World!n";
}
preprocessor directive identifier
Main function
integer
Program Body
standard output stream
output operator
newline character
Messege to print

3. VARIABLES AND THEIR DECLARATIONS
• A variable is a symbol that represents a storage location in the computer’s memory
• Every variable in a C++ program must be declared before it is used.The syntax is
specifier type name initializer;
int main()
{ // prints "m = 44 and n = 77":
int m, n;
m = 44; // assigns the value 44 to the variable m
cout << "m = " << m;
n = m + 33; // assigns the value 77 to the variable n
cout << " and n = " << n << endl;
}
optional keyword
such as const
C++ data types
such as int,
name of the
variable
Optional initialization
clause such as =44
The scope of a variable extends from its point of declaration to the end of the immediate block in which it is
declared or which it controls.

4. PROGRAM TOKENS
• A computer program is a sequence of elements called tokens.
• Include
• Keywords such as int,
• identifiers such as main,
• punctuation symbols such as {,
• operators such as <<.
int main()
{ // prints "n = 44":
int n=44;
cout << "n = " << n << endl;
}
19 tokens :
1. “int”,
2. “main” ,
3. “(”,
4. “)”,
5. “{”,
6. “int”,
7. “n”,
8. “=”,
9. “44”,
10. “;”,
11. “cout”,
12. “<<”,
13. “"n = "”,
14. “<<”,
15. “n”,
16. “<<”,
17. “endl”,
18. “;”,
19. “}”.
int main()
{ // THIS SOURCE CODE HAS AN ERROR:
int n=44
cout << "n = " << n << endl;
}
compiler issued the following error message:
Error : ';' expected
Testing.cpp line 4 cout << "n = " << n << endl;

5. INITIALIZING VARIABLES
• In most cases it is wise to initialize variables where they are declared
int main()
{ // prints "m = ?? and n = 44":
int m; // BAD: m is not initialized
int n= 44;
cout << "m = " << m << " and n = " << n << endl;
}
m = -2107339024 and n = 44
In larger programs, uninitialized variables can cause troublesome errors.

6. OBJECTS, VARIABLES, AND
CONSTANTS
• Object - a contiguous region of memory that has
• Address - the memory address of its first byte,
• Size - the number of bytes that it occupies in memory,
• Type - how the bits are to be interpreted,
• Value - the constant determined by the actual bits stored in its memory location
int n = 22;
• Memory address 0x3fffcd6 (address is a hexadecimal number),
• Size 4
• Type int
• Value 22

7. THE INPUT OPERATOR(>> )
The input operator >> (also called the get operator or the extraction operator)
int main()
{ // tests the input of integers,floats,and characters:
int m,n;
cout << "Enter two integers: ";
cin >> m >> n;
cout << "m = " << m << ", n = " << n << endl;
double x,y,z;
cout << "Enter three decimal numbers: ";
cin >> x >> y >> z;
cout << "x = " << x << ", y = " << y << ", z = " << z << endl;
char c1,c2,c3,c4 ;
cout << "Enter four characters: ";
cin >> c1 >> c2 >> c3 >> c4;
cout << "c1 = " << c1 << ",c 2 = " << c2 << ", c3 = " << c3 << ", c4 = " << c4 << endl;
}
Enter two integers: 22 44
m = 22, n = 44
Enter three decimal numbers: 2.2 4.4 6.6
x = 2.2,y = 4.4,z = 6.6
Enter four characters: ABCD
c1 = A, c2 = B, c3 = C, c4 = D

8. HOMEWORK/LABWORK
Do the complete Exercise of Chapter 1 in
your notebooks