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Chapter 01: Introduction to Computer Programming
Dr. Anis Koubaa
Apr 19, 20231
CS140: C++ Programming 1
Al-Imam Mohammad Ibn Saud UniversityAl-Imam Mohammad Ibn Saud University
Computer Programming
2
Software Instructions to command computer to perform
actions and make decisions Hardware Standardized version of C++
United States American National Standards Institute (ANSI)
Worldwide International Organization for Standardization (ISO)
Structured programming Object-oriented programming
What is a Computer?
3
Computer Device capable of performing computations and
making logical decisions Computer programs
Sets of instructions that control computer’s processing of data
Hardware Various devices comprising computer
Keyboard, screen, mouse, disks, memory, CD-ROM, processing units, …
Software Programs that run on computer
C++ Standard Library
4
C++ programs Built from pieces called classes and functions
C++ standard library Rich collections of existing classes and functions
“Building block approach” to creating programs “Software reuse”
Basics of a Typical C++ Environment
C++ systems Program-development environment Language C++ Standard Library
5
Basics of a Typical C++ Environment
6
Phases of C++ Programs:
1. Edit
2. Preprocess
3. Compile
4. Link
5. Load
6. Execute
Loader
PrimaryMemory
Program is created inthe editor and storedon disk.
Preprocessor programprocesses the code.
Loader puts programin memory.
CPU takes eachinstruction andexecutes it, possiblystoring new datavalues as the programexecutes.
Compiler
Compiler createsobject code and storesit on disk.
Linker links the objectcode with the libraries,creates a.out andstores it on disk
PrimaryMemory
Introduction to C++ Programming
7
C++ language Facilitates structured and disciplined approach to
computer program design Following several examples
Illustrate many important features of C++ Each analyzed one statement at a time
Structured programming Object-oriented programming
First Program in C++
Printing a Line of Text
8
A Basic C++ Program
9
1 // Fig. 1.2: fig01_02.cpp
2 // A first program in C++.
3 #include <iostream>
4
5 // function main begins program execution
6 int main()
7 {
8 std::cout << "Welcome to C++!\n";
9
10 return 0; // indicate that program ended successfully
11
12 } // end function main
Welcome to C++!
Simple Program: Printing a Line of Text
10
Comments Document programs Improve program readability Ignored by compiler Single-line comment
Begin with //
Preprocessor directives Processed by preprocessor before compiling Begin with #
11
Basics of a Typical C++ Environment Input/output
cin Standard input stream (like Read) Normally keyboard
cout Standard output stream (like Write) Normally computer screen
cerr Standard error stream Display error messages
A Simple Program: Printing a Line of Text
12
Standard output stream object std::cout “Connected” to screen <<
Stream insertion operator Value to right (right operand) inserted into output stream
Namespace std:: specifies using name that belongs to
“namespace” std std:: removed through use of using statements
Escape characters \ Indicates “special” character output
A Simple Program:Printing a Line of Text
13
Escape Sequence Description
\n Newline. Position the screen cursor to the beginning of the next line.
\t Horizontal tab. Move the screen cursor to the next tab stop.
\r Carriage return. Position the screen cursor to the beginning of the current line; do not advance to the next line.
\a Alert. Sound the system bell.
\\ Backslash. Used to print a backslash character.
\" Double quote. Used to print a double quote character.
Printing line with multiple statements
14
1 // Fig. 1.4: fig01_04.cpp
2 // Printing a line with multiple statements.
3 #include <iostream>
4
5 // function main begins program execution
6 int main()
7 {
8 std::cout << "Welcome ";
9 std::cout << "to C++!\n";
10
11 return 0; // indicate that program ended successfully
12
13 } // end function main
Welcome to C++!
Printing multiple lines with a single statement
15
1 // Fig. 1.5: fig01_05.cpp
2 // Printing multiple lines with a single statement
3 #include <iostream>
4
5 // function main begins program execution
6 int main()
7 {
8 std::cout << "Welcome\nto\n\nC++!\n";
9
10 return 0; // indicate that program ended successfully
11
12 } // end function main
Welcome
to
C++!
Using newline characters to print on multiple lines.
Another Simple Program
Adding Integers
16
17
1 // Fig. 1.6: fig01_06.cpp2 // Addition program.3 #include <iostream>4 5 // function main begins program execution6 int main()7 {8 int integer1; // first number to be input by user 9 int integer2; // second number to be input by user 10 int sum; // variable in which sum will be stored11 12 std::cout << "Enter first integer\n"; // prompt13 std::cin >> integer1; // read an integer14 15 std::cout << "Enter second integer\n"; // prompt16 std::cin >> integer2; // read an integer17 18 sum = integer1 + integer2; // assign result to sum19 20 std::cout << "Sum is " << sum << std::endl; // print sum21 22 return 0; // indicate that program ended successfully23 24 } // end function main
Use stream extraction operator with standard input stream to obtain user input.
18
Enter first integer45Enter second integer72Sum is 117
Another Simple Program:Adding Two Integers
19
Variables Location in memory where value can be stored Common data types
int - integer numbers char - characters double - floating point numbers
Declare variables with name and data type before useint integer1;int integer2;int sum;
Can declare several variables of same type in one declaration Comma-separated listint integer1, integer2, sum;
Another Simple Program:variable and data type
20
Variables Variable names
Valid identifier Series of characters (letters, digits, underscores) Cannot begin with digit Case sensitive
boolbool A boolean variable is defined to be of type bool. A boolean has a value of true or false which
correspond to 1 or 0 accordingly.bool correct = true;
bool Yes; correct = false; Yes = true;
Another Simple Program:variable and data type
21
CharactersCharacters
A character variable is defined to be of type char.
A character variable occupies a single byte which contains the code for
the character. This code is a numeric value and depends on the character
coding system being used .
e.g. character A has the ASCII code 65
the character a has the ASCII code 97.
A literal character is written by enclosing the character between a pair of
single quotes (e.g., 'A').
char ch = 'A';
a character variable may be specified to be signed (by default on most
systems) or unsigned.
signed character : -128 through 127
unsigned character : 0 through 255
Another Simple Program:variable and data type
22
Integer:Integer: An integer variable may be defined to be of
type: short,
int, or long.
The only difference is that an int uses more or at least the same number of bytes as a short, and a long uses more or at least the same number of bytes as an int (i.e. a short may uses 2 bytes, an int also 2 bytes, and a long 4 bytes.)
short int age = 20;int salary = 65000;long int price = 4500000;
Another Simple Program:variable and data type
23
Integer:Integer: By default, an integer variable is assumed to
be signed (i.e., has positive as well as negative values).
An integer can be defined to be unsigned as
well as signed type
unsigned short int age = 20;unsigned int salary = 65000;unsigned long int price = 4500000;
Another Simple Program:variable and data type
24
Real Numbers A real variable may be: float or double. The difference is in the number of bytes which therefore
offers a greater range and accuracy for representing real numbers (e.g.; a float may uses 4 bytes and a double may uses 8 bytes).
float interestRate = 0.06; double pi = 3.141592654;
In addition to the decimal notation used so far, literal reals
may also be expressed in scientific notation. For example,
0.002164 may be written in the scientific notation as:
2.164E-3 or 2.164e-3
Which is interpreted as follows: 2.164E-3 = 2.164 × 10-3
Input methods
25
Input methods Input stream object
>> (stream extraction operator) Used with std::cin Waits for user to input value, then press Enter (Return)
key Stores value in variable to right of operator
Converts value to variable data type
= (assignment operator) Assigns value to variable Binary operator (two operands) Example:
sum = variable1 + variable2;
26
What happens in the memory?
27
Memory Concepts
28
Variable names Correspond to actual locations in computer's
memory Every variable has name, type, size and value When new value placed into variable, overwrites
previous value Reading variables from memory nondestructive
Memory Concepts
29
std::cin >> integer1; Assume user entered 45
std::cin >> integer2; Assume user entered 72
sum = integer1 + integer2;
integer1 45
integer1 45
integer2 72
integer1 45
integer2 72
sum 117
Arithmetic
30
Arithmetic calculations *
Multiplication /
Division Integer division truncates remainder
7 / 5 evaluates to 1
% Modulus operator returns remainder
7 % 5 evaluates to 2
Arithmetic
31
Rules of operator precedence Operators in parentheses evaluated first
Nested/embedded parentheses Operators in innermost pair first
Multiplication, division, modulus applied first Operators applied from left to right
Addition, subtraction applied last Operators applied from left to right
Operator(s) Operation(s) Order of evaluation (precedence)
() Parentheses Evaluated first. If the parentheses are nested, the expression in the innermost pair is evaluated first. If there are several pairs of parentheses “on the same level” (i.e., not nested), they are evaluated left to right.
*, /, or % Multiplication Division Modulus
Evaluated second. If there are several, they re evaluated left to right.
+ or - Addition Subtraction
Evaluated last. If there are several, they are evaluated left to right.
Decision Making: Equality and Relational Operators
32
if structure Make decision based on truth or falsity of
condition If condition met, body executed Else, body not executed
Equality and relational operators Equality operators
Same level of precedence Relational operators
Same level of precedence Associate left to right
Decision Making: Equality and Relational Operators
33
Standard algebraic equality operator or relational operator
C++ equality or relational operator
Example of C++ condition
Meaning of C++ condition
Relational operators
> > x > y x is greater than y
< < x < y x is less than y
>= x >= y x is greater than or equal to y
<= x <= y x is less than or equal to y
Equality operators
= == x == y x is equal to y
!= x != y x is not equal to y
Decision Making: Equality and Relational Operators
34
using namespace std; Eliminate use of std:: prefix Write cout instead of std::cout
35
1 // Fig. 1.14: fig01_14.cpp2 // Using if statements, relational3 // operators, and equality operators.4 #include <iostream>5 6 using std::cout; // program uses cout7 using std::cin; // program uses cin 8 using std::endl; // program uses endl 10 // function main begins program execution11 int main()12 {13 int num1; // first number to be read from user14 int num2; // second number to be read from user15 16 cout << "Enter two integers, and I will tell you\n"17 << "the relationships they satisfy: ";18 cin >> num1 >> num2; // read two integers19 20 if ( num1 == num2 ) 21 cout << num1 << " is equal to " << num2 << endl;22 23 if ( num1 != num2 )24 cout << num1 << " is not equal to " << num2 << endl;25
36
26 if ( num1 < num2 )27 cout << num1 << " is less than " << num2 << endl;28 29 if ( num1 > num2 )30 cout << num1 << " is greater than " << num2 << endl;31 32 if ( num1 <= num2 )33 cout << num1 << " is less than or equal to "34 << num2 << endl;35 36 if ( num1 >= num2 )37 cout << num1 << " is greater than or equal to "38 << num2 << endl;39 40 return 0; // indicate that program ended successfully41 42 } // end function main
Enter two integers, and I will tell you
the relationships they satisfy: 22 12
22 is not equal to 12
22 is greater than 12
22 is greater than or equal to 12
37
Enter two integers, and I will tell you the relationships they satisfy: 7 7 7 is equal to 7 7 is less than or equal to 7 7 is greater than or equal to 7
Exercise
38
Write a program which reads 4 numbers and print the biggest and the lowest numbers
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