CS174Week2

Report
Introduction to C++ Programming
Lesson Plan
 Knowledge of simple C++ program
 Write simple input/output statements
 Knowledge of data types, variable declaration, arithmetic
operators
Simple C++ Program by example
/* This is HelloWorld program in C++ */
#include <iostream>
using namespace std;
int main()
{
cout << "Hello World!\n This is my first C++ program\n";
return 0;
}
Simple C++ Program by example
/* This is HelloWorld program in C++ */
#include <iostream>
This is C++
using namespace std;
comment
int main()
{
cout << "Hello World!\n This is my first C++ program\n";
return 0;
}
C++ comments
 Comments: Must-have, to explain what a programmer is doing
while coding
Single line comments: // this is my comment
Multiple line comments:
/*
This is my comment
This also is my comment
*/
Simple C++ Program by example
/* This is HelloWorld program in C++ */
#include <iostream>
This is C++
using namespace std;
Preprocessor
directive
int main()
{
cout << "Hello World!\n This is my first C++ program\n";
return 0;
} 1. Comment out #include <iostream> from your hello.cpp
2. Save and Compile it
3. Describe the error
Simple C++ by example
 Preprocessor directive:
 This is processed by the preprocessor before the program is
compiled.
 Notifies the preprocessor to include in the program the content
of corresponding header file from C++ header library (i.e *.h
file)
Simple C++ Program by example
/* This is HelloWorld program in C++ */
#include <iostream>
Using
using namespace std;
declarations
int main()
{
cout << "Hello World!\n This is my first C++ program\n";
0; out using std::cout from your hello.cpp
1.return
Comment
}2. Save and Compile it
3. Describe the error
4. Change cout to be std:: cout, save and compile
Simple C++ Program by example
 Using declarations eliminates the needs to repeat
std::<prefix>
 So we use:
 using std::cout; // for program uses cout
 using std::cin; // for program uses cin
 using std::endl; // for program uses endl;
….
Or we can use:
using namespace std;
Simple C++ Program by example
/* This is HelloWorld program in C++ */
#include <iostream>
using namespace std;
int main()
{
function
in is my first C++ program\n";
cout << "HelloMain
World!\n
This
C++
return 0;
}
Simple C++ Program by example
• Syntax:
int main() {
}
• Main function is a part of every C++ Program
• Exactly one function in every program must be named main
• int: means return an integer (in this context only)
1. Rename main to Main in your hello.cpp
2. Save and Compile it
3. Describe the error
Simple C++ Program by example
/* This is HelloWorld program in C++ */
#include <iostream>
using namespace std;
int main()
{
cout << "Hello World!\n This is my first C++ program\n";
return 0;
}
C++ statement
Simple C++ Program by example
 Every C++ statement must end with ;
 Preprocessor directives do not end with ;
 << operator: stream insertion operator
 Insert the value on the right to the output stream
 \n (escape sequence): new line
Simple C++ Program by example
/* This is HelloWorld program in C++ */
#include <iostream>
using namespace std;
int main()
{
cout << "Hello World!\n This is my first C++ program\n";
return 0;
Return
}
statement to exit
a function
Steps to develop a C++ Program
Editor
Preprocessor
Compiler
Linker
“On-the-fly” questions
/* This is a valid C++ comment /*
True
b. False
a.
“On-the-fly” questions
/* This is a valid C++ comment /*
True
b. False
a.
“On-the-fly” question
 Every C++ statement ends with a(n):
a. }
b. {
c. ;
d. return
“On-the-fly” question
 Every C++ statement ends with a(n):
a. }
b. {
c. ;
d. return
“On-the-fly” question
Every C++ program begins execution at the function
a. Main
b. MAIN
c. static main
d. main
“On-the-fly” question
Every C++ program begins execution at the function
a. Main
b. MAIN
c. static main
d. main
Variable declaration
Syntax:
<data type> <variable_name>;
If more than one variable has the same data type:
<data type> <name1>, <name2>..;
Fundamental numerical data types
Name
char
short int
(short)
Description
Size*
Character or small integer.
1byte
signed: -128 to 127
unsigned: 0 to 255
Short Integer.
2bytes
signed: -32768 to 32767
unsigned: 0 to 65535
int
Integer.
4bytes
long int
(long)
Long integer.
4bytes
Floating point number.
4bytes
float
double
long
double
Range*
signed: -2147483648 to
2147483647
unsigned: 0 to 4294967295
signed: -2147483648 to
2147483647
unsigned: 0 to 4294967295
+/- 3.4e +/- 38 (~7 digits)
Double precision floating point number. 8bytes
+/- 1.7e +/- 308 (~15 digits)
Long double precision floating point
number.
+/- 1.7e +/- 308 (~15 digits)
8bytes
Variable names
 It must be a legal identifier.
 It must not be a keyword, a boolean literal (true or
false), or the reserved word.
 It must be unique within its scope.
Identifier
 A valid identifier is a sequence of one or more letters, digits or
underscore characters (_).
 Identifiers may only begin with a letter, or _.
 Keyword:
 http://www.cplusplus.com/doc/tutorial/variables/
 C++ is case sensitive language
Example
int firstNumber;
int secondNumber;
int sum;
All variables in C++ MUST be
declared before being used
int firstNumber, secondNumber, sum;
Reading a value from keyboard
 Example:
cin >> firstNumber;
A cin statement uses the input stream object cin (of
namespace std) and the stream extraction operator,
>>, to obtain a value from the keyboard.
Usually you will need a prompt it directs the user to take
a specific action before putting cin statement
Assignment statement
<variable name> = <expression>;
Example:
sum = firstNumber + secondNumber;
Or
sum = 6+7;
Arithmetic Expression
 Any expression involving numerical value is called arithmetic
expression
For example:
x+15
y /16
Arithmetic operators
 Addition: +
x+y
 Subtraction: x-y
 Multiplication: *
x*y
 Division: /
x/y
 Modulo: %
x%y
Arithmetic
 Most programs perform arithmetic calculations.
 The asterisk (*) indicates multiplication.
 The percent sign (%) is the modulus operator:
 C++ provides the modulus operator, %, that yields
the remainder after integer division.
 The modulus operator can be used only with integer
operands.
 Integer division (i.e., where both the numerator and the
denominator are integers) yields an integer quotient.
 Any fractional part in integer division is discarded
(i.e., truncated)—no rounding occurs.
Arithmetic
 C++ applies the operators in arithmetic expressions in a
precise sequence determined by the following rules of
operator precedence, which are generally the same as those
followed in algebra.
Arithmetic
 There is no arithmetic operator for exponentiation in C++,
so x2 is represented as x * x.
 As in algebra, it’s acceptable to place unnecessary parentheses
in an expression to make the expression clearer.
 These are called redundant parentheses.
Constant and variables
 Constant:
 Value it contains doesn’t change
 Two ways to declare a constant in C++:
#define <constant name> <value>; // using
preprocessor directives
const <datatype> <constant name>; // inside
the program
 Variables:
 Value it contains may vary
int sum;
 sum =0;
 sum = firstNumber + secondNumber;
Operator <<
 Using multiple stream insertion operators (<<) in a single
statement is referred to as concatenating, chaining or
cascading stream insertion operations.
 Calculations can also be performed in output statements.
Memory Concepts
 Variable names such as firstNumber,
secondNumber and sum actually correspond to
locations in the computer’s memory.
 Every variable has a name, a type, a size and a value.
 When a value is placed in a memory location, the
value overwrites the previous value in that location;
thus, placing a new value into a memory location is
said to be destructive.
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