0. Introduction to C++ computers and programming
CMPT 129
© Janice Regan, CMPT 129, 2017

1. Summary CHAPTER 1 CHAPTER 2 What is a program? Programming languages
Hardware and Software
What is a program?
Programming languages
Program design and implementation
CHAPTER 2
Structure of a C++ program
Parts of a C++ program
Variables, Constants and Literals
© Janice Regan, CMPT 129, 2017

2. Hardware and Software Hardware refers to the computer components.
Peripheral Input and output devices
Processing and storage devices
A computer is a collection of integrated hardware components
Software refers to the programs that describe the steps we want the computer to perform.
A program is an ordered series of steps that solve a problem using the computer
© Janice Regan, CMPT 129, 2017

3. Computer Hardware CPU – Memory – Secondary Storage Control Unit
ALU – Arithmetic and logic unit
Registers
Cache
Memory –
Secondary Storage
Main Memory
ROM - Read only memory
RAM – Random access memory
Input
Devices ?
Internal
Memory
External
Memory
CPU
Control\
Unitr
Output
Devices ?
ALU
ALU
Cache/
Memory
© Janice Regan, CMPT 129, 2017

4. Central Processing Unit (CPU)
Performs arithmetic
The processor adds, subtracts, multiplies and divides binary numbers using the Arithmetic Logic Unit, ALU
Makes comparisons
The processor can check if two “numbers” are equal, and determine if one is “larger” or “smaller” than the other
Moves bits (binary digits)
Knows how to access any RAM (or ROM) address
Can copy data to or from any memory address and its own onboard memory
© Janice Regan, CMPT 129, 2017

5. Information storage Primary Storage: RAM, ROM
requires power to store information
Internal storage
Secondary Storage: DVD, thumb drives, SD cards …
Less expensive (so more plentiful)
Information persists even without power
Stores information that is loaded into primary storage (like programs and data) to be used
Internal or external storage
© Janice Regan, CMPT 129, 2017

6. Software: Operating System
Common operating systems
Windows
Mac O/S
Linux
The operating system manages applications
Shares the memory, cpu and other facilities in your computer between applications and utility programs you are running at the “same” time
Provides services like your user interface
© Janice Regan, CMPT 129, 2017

7. Example: Graphical UI (GUI)
Windows explorer
© Janice Regan, CMPT 129, 2017

8. Algorithm A sequence of precise instructions that leads to a solution
Order of instructions is important
Amount of detail must be appropriate
© Janice Regan, CMPT 129, 2017

9. Program Design Problem Solving phase Define the problem
Design the algorithm to solve the problem
Test the algorithm
Implementation
Translate the algorithm to a computer language like C or C++
Test the program extensively
© Janice Regan, CMPT 129, 2017

10. Testing? To test you must Know how to run a program
Know how to debug a program
Understand how to identify bugs
Know how to design the tests to run
© Janice Regan, CMPT 129, 2017

11. Creating an Executable for a C++ Program
Linker
Integrates object code from other sources with the object code for this source file
C++ Program in Text file
(source file)
saved on disk
Machine language
Version of source file (object file)
saved on disk
Other
object files
PREPROCESSOR
modifies source file
by executing all statements starting with #
COMPILER
Converts preprocessed source file to an object file
Executable file for the C++ program
saved on disk
© Janice Regan, CMPT 129, 2017

12. RUNNING an Executable for a C++ Program
Executable file for the C++ program
saved on disk
Outputs results
LOADER
Copies the executable file to RAM memory and starts execution
CPU
Loads and executes instructions in the executable program
Reads data
© Janice Regan, CMPT 129, 2017

13. Developing a C++ Program
Correct
Errors
Editor,
Enter/modify
C++ program
Input
data
Output
correct
results
Find Syntax
and some
SemanticErrors
Compile
Object
File
(binary)
CPU
Run time errors
Link Errors Reported:
Loader
Copies
Executable
And Runs
Linker
Resolves
References
Executable File
(binary)
Other
Object Files
© Janice Regan, CMPT 129, 2017
Debugged Executable Code

14. Summary: Types of Errors
Syntax errors
Errors in syntax, how words are combined and used
reported by the compiler
Semantic errors
Errors in the meaning of words,
Reported by the linker (linker errors)
Reported by the compiler (compile time errors)
Found at execution time (run-time errors)
Logic errors
Errors causing incorrect results, not reported
Errors causing program failure (run-time errors)
© Janice Regan, CMPT 129, 2017

15. Hello World: your first program
// My first C++ program
// make the computer print the string “Hello world”
// connect to any necessary libraries or objects
#include <iostream>
using namespace std;
// the main function, implements the algorithm to solve the problem
// the main function may use functions from included libraries
int main ( ) {
cout << "Hello, world!" << endl; // Prints Hello world
return 0; }
© Janice Regan, CMPT 129, 2017

16. Comments
Comments are essential to clearly explain the purpose of your code and the methods of implementation used
When you use another programmer’s code
When another programmer tries to use your code
When you try to use your own code after months or years
Comments make it is much easier to figure out how things work in existing code.
Comments are not “executed”
© Janice Regan, CMPT 129, 2017

17. Good AND BAD Comments
Give ADDITIONAL information not obvious from the code
// This program calculates the first 20 primes
Do not translate code into English
C = A+B // Add A to B (BAD COMMENT)
© Janice Regan, CMPT 129, 2017

18. C++, self documenting? A = b + c; // b and c are numbers of people
Better to write
TotalStudents = FullTimeStudents + OtherStudents;
Code is more readable when variables used have names that describe what they contain
© Janice Regan, CMPT 129, 2017

19. Hello World: C++
// My first C++ program
// make the computer print the string “Hello world”
// connect to any necessary libraries or objects
#include <iostream> // iostream is a stream object used to read/write
using namespace std;
// the main function, implements the algorithm to solve the problem
// the main function may use functions from included libraries
// the iostream stream object includes read and write functions like cout
int main ( ) {
cout << "Hello, world!" << endl; // Prints Hello world
return 0; }
© Janice Regan, CMPT 129, 2017

20. C++ Libraries and objects
#include <iostream>
The # at the beginning of the line indicates that the command is for the C preprocessor (a preprocessor directive)
The C preprocessor puts the prototypes (function descriptions) for the functions in the library or object into your program instead of the line of code above then passes the resulting code to the compiler
If the preprocessor directive to include the library or object is not part of your program, your program will not be able to use the functions in the library or object
© Janice Regan, CMPT 129, 2017

21. Objects and Libraries
In our first C++ program we are using the iostream stream object (library).
This object is used to read from the keyboard and write to the screen
Any C++ program that reads or writes information should include the iostream stream object
Later we will look at the details of what we can do with iostream.
© Janice Regan, CMPT 129, 2017

22. Name Spaces, C++ using namespace std;
Indicates you wish to use the standard namespace
In large advanced programs it is possible that you want to use additional namespaces to prevent naming conflicts.
For this course you will always use the standard namespace and you will always have this line in your C++ programs
© Janice Regan, CMPT 129, 2017

23. Hello World: C++
// My first C++ program
// make the computer print the string “Hello world”
// connect to any necessary libraries and objects
#include <iostream> // iostream is a object used to read and write
using namespace std;
// the main function, implements the algorithm to solve the problem
// the main function may use functions from included libraries
// the iostream object includes read and write functions like cout
int main ( ) {
cout << "Hello, world!" << endl; // Prints Hello world
return 0; }
© Janice Regan, CMPT 129, 2017

24. Creating a C++ main function
int main ( ) {
// Body of the main function
return 0; }
The head of the main function is indicated by the statement int main ( )
The body of the main function (the code that accomplishes the task of the main function) is enclosed in { }.
The convention used in this course in to put each of the { } on its own separate line.
© Janice Regan, CMPT 129, 2017

25. Body of the C++ MAIN FUNCTION
For our first program the body consists of a single line of code
cout << "Hello, world! " << endl;
cout prints to the screen
Everything inside the " " is printed
endl means move to the start of the next line before printing anything else
© Janice Regan, CMPT 129, 2017

26. The return statement
The type at the start of the head of the function indicates the type of the value to be returned by the function.
At one or more places in the function the function will complete its task.
After the task is completed the result should be returned to the calling function (for main the OS or the IDE is the calling function)
The return statement indicates the value to return.
The value of a literal constant or a variable will be returned ( e.g. return 0; or return A; )
© Janice Regan, CMPT 129, 2017

27. LANGUAGE ELEMENTS: Tokens
Token: smallest individual language elements in a program
Types of tokens include
Reserved words
Variables,
Named Constants and Literal Constants
Literals
Operators
Punctuation
© Janice Regan, CMPT 129, 2017

28. Why variables and named constants?
Calculate the diameter of a circle
First you need the diameter
On paper write the numbers down the value of the diameter to record it (store it)
In a program those two numbers can be put into a variable to record it
Next you need the value of the constant π
π is a constant, its value should not change during the execution of your program
The value of π can be recorded in a named constant
A named constant is a special type of variable whose value is set once and cannot be changed
© Janice Regan, CMPT 129, 2017

29. Constants and Variables
Each constant or variable represents a specific item in the problem the program solves and is associated with
a memory cell used to hold its value
a unique identifier or name
a data type (that is consistent with the value)
The value of a named constant does not change during execution of the program
The value of a variable may be changed during the execution of a program.
© Janice Regan, CMPT 129, 2017

30. C++ Identifiers Names of program components: IMPORTANT!!!
Variables, Constants
Structures, arrays, functions, … (more later)
IMPORTANT!!!
. C++ is case sensitive
The following identifiers (names ) are NOT the same
Toy toy TOY
© Janice Regan, CMPT 129, 2017

31. Legal C++ Identifiers Must contain only:
Letters (upper and lower case)
Digits (0-9)
The underscore character ( _ )
Identifiers must begin with a letter or an _
Identifiers beginning with an _ are, by convention, used for specific purposes and should be avoided in general use
© Janice Regan, CMPT 129, 2017

32. Reserved words
In a computer language there are always a number of special words that are used as instructions and definitions in the language. These are called
reserved words
Reserved words cannot be used as identifiers
© Janice Regan, CMPT 129, 2017

33. Reserved words in C++
A reserved word is a special word that gives the compiler a specific instruction it can understand (summary in text)
asm, auto, bool, break, case, catch, char, const, class, continue
default, delete, do, double, else, enum, explicit, export, extern
false, float, for, friend, goto, if, inline, int, long, mutable, throw
namespace, new, operator, private, protected, public, register
return, short, signed, sizeof, static, struct, switch, template, this
true, try, typedef, union, unsigned, using, virtual, void, volatile, while
© Janice Regan, CMPT 129, 2017

34. More About C++ Identifiers
Can divide identifiers into two groups
Standard Identifiers:
Identifiers defined by the compiler that are not parts of the C++ language definition
This include identifiers used as names of functions in the standard C++ libraries
User (programmer) defined Identifiers:
Names the programmer chooses for quantities, functions, etc. used in their own programs
© Janice Regan, CMPT 129, 2017

35. Which Are Legal C++ Identifiers?
cycle
A!star
int
Score
Y-Z
Trial#2
This_One
$MyProgram
FOR
3constant_values
“MaxScores”
_External_Prog
Mary’s
StarChart
© Janice Regan, CMPT 129, 2017

36. More About C++ Identifiers
An identifier should be descriptive. It makes your code much easier to understand and maintain
sideLength is much clearer than sl
But keep your names a reasonable length
The maximum number of significant characters in an identifier is determined by the operating system and compiler used.
Programming style for this course:
Used identifiers that describe the contents of the variable or constant
© Janice Regan, CMPT 129, 2017

37. Named Constants and Variables
Each constant or variable represents a specific item in the problem the program solves and is associated with
a memory cell used to hold its value
a unique identifier or name
a data type (that is consistent with the value)
The value of a named constant does not change during execution of the program
The value of a variable may be changed during the execution of a program.
© Janice Regan, CMPT 129, 2017

38. Types of named Constants and Variables
A Data Type is
A set of values plus a set of operations on those values
A crucial concept on modern programming
The data type of a variable or named constant also determines how the variable’s value will be represented in memory
Variables of several types can have numerical values
Variables of other types have values that are characters, or logical values.
© Janice Regan, CMPT 129, 2017

39. Types with Numerical Values
Two classes of numerical values
Integer values are whole numbers
1, 243, -777
C++ types: int, unsigned int, long long int, short int
Floating point values have a fractional part
987.4, , 0.123,
C++ types: float, double, long double
Integers and floating point numbers are represented differently inside the computer
Integers are represented as 2s complement binary numbers
Floating point numbers are represented in exponential form, the mantissa and exponent are both expressed in binary
Can talk a very little bit about Ada strong typing, it does not automatically convert values for you.
© Janice Regan, CMPT 129, 2017

40. types with non numerical values
Characters
char Holds a single character
char xchar = ‘8’; char yesno = ‘y’;
String
string Holds a sequence of characters
string name = "Jane"; string phoneNum= " ";
Boolean
Bool Holds values of true of false
bool testResult = true; bool notEqualOne = false;
© Janice Regan, CMPT 129, 2017

41. Declaring the variables you need
A first step in building the body of your main function is the declaration of the variables you will need to execute your algorithm.
To declare a variable we need to
choose an identifier as the name of the variable.
choose what the type of the variable is.
In C++ all variables MUST be declared before they are used.
© Janice Regan, CMPT 129, 2017

42. Program - ADD two numbers
#include <iostream>
using namespace std;
int main() {
// Declare variables.
double number1;
double number2;
double sum;
// Initialize variables
number2 = 45.7;
number1 = 473.9;
// Calculate and print the sum.
sum = number1 + number2;
cout << " The sum is ” << sum << endl;
// Return successful termination indicator
return 0; }
Standard identifiers
© Janice Regan, CMPT 129, 2017

43. Declaration of Variables
Programming style for this course:
Declare one variable or constant per statement
Declare all variables at the start of the function.
Examples:
int myintegervalue;
double scalefactor;
float temperature;
auto active; //C++ 11 and later
© Janice Regan, CMPT 129, 2017

44. Initialization of Variables
Memory locations associated with variables should have their values defined before the start of program execution.
Using uninitialized variables can produce unpredictable results
Programming style for this course:
Initialize all variables at the start of your executable code
Initialize when or just after your variables have been declared
© Janice Regan, CMPT 129, 2017

45. Program - aDD two numbers
#include <iostream>
using namespace std;
int main(void) {
// Declare variables.
double number1;
double number2;
double sum;
// Initialize variables
number2 = 45.7;
number1 = 473.9; sum = 0.0;
// Calculate and print the sum.
sum = number1 + number2;
cout << "The sum is " << sum << endl;
// Return successful termination indicator
return 0; }
© Janice Regan, CMPT 129, 2017

46. Program - ADD two numbers
#include <iostream>
using namespace std;
int main(void) {
// Calculate and print the sum.
sum = number1 + number2;
cout << "The sum is " << sum << endl;
// Return successful termination indicator
return 0; }
// Declare and initialize variables.
double number1 = 473.9;
double number2 = 45.7;
double sum=0.0;
© Janice Regan, CMPT 129, 2017

47. Named constants and Literal Constants
Cannot change values during execution
Called "literals" because you "literally typed" them in your program!
CONSTANTS
Literal Constants do not have identifiers (names), they are used directly in the C++ code
Named Constants do have identifiers (names)
© Janice Regan, CMPT 129, 2017

48. Examples of Literal Constants
2 // int
17LL // long long int
888L // long int
5.75 // double
`Z` // char
"Hello World" // string
true // bool
© Janice Regan, CMPT 129, 2017

49. Program - ADD two numbers
#include <iostream>
using namespace std;
int main(void) {
// Declare variables.
double number1, number2;
double sum;
// Initialize variables
number2 = 45.7;
number1 = 473.9;
// Calculate and print the sum.
sum = number1 + number2;
cout << “The sum is ” << sum << endl;
// Return successful termination indicator
return 0; }
double literal constants
String literal constant
© Janice Regan, CMPT 129, 2017

50. Named Constants Naming your constants Use named constants instead
Literal constants are "OK", but provide little meaning
e.g., seeing in a program, tells nothing about what it represents
Use named constants instead
Meaningful name to represent data
const double PI = ;
Called a "declared constant" or "named constant"
Now use it’s name wherever needed in program
Added benefit: changes to value need only be made once
© Janice Regan, CMPT 129, 2017

51. Programming style: summary
Use descriptive identifiers
Declare and initialize all variables at the start of each program (function)
Easier to keep track of variables, they will always be available for the whole program (function)
You will not have problems with undeclared variables
Use named constants, not literal constants
Easier to keep track of what the constants mean
Easier to keep track of what the constants values are
Easier to change all instances of the same constant
© Janice Regan, CMPT 129, 2017

52. Binary Arithmetic Operators
+ addition
- subtraction
* multiplication
/ division
% modulus or remainder (only for integers, 5%2=1)
Evaluated left to right (C and C++)
We don’t get into details here, wrt integer division and exponentiation
If they ask, Integer division returns an integer result (truncated toward zero)
If left side of ** is integer, right side must be nonnegative (Natural).
In any case RHS of exponentiation is an integer.
© Janice Regan, CMPT 129, 2017

53. Unary Arithmetic Operators
+ positive
- negative
++ increment
-- decrement
~ ones complement
Evaluated right to (C and C++)
We don’t get into details here, wrt integer division and exponentiation
If they ask, Integer division returns an integer result (truncated toward zero)
If left side of ** is integer, right side must be nonnegative (Natural).
In any case RHS of exponentiation is an integer.
© Janice Regan, CMPT 129, 2017

54. Expressions in C++
An expression can be a single variable, or can be a series of variables combined using operators
Arithmetic expressions manipulate numeric variables following the rules of algebra
The two variables or constants combined using a binary arithmetic operator should have the same type
Otherwise conversions are needed
We don’t get into details here, wrt integer division and exponentiation
If they ask, Integer division returns an integer result (truncated toward zero)
If left side of ** is integer, right side must be nonnegative (Natural).
In any case RHS of exponentiation is an integer.
© Janice Regan, CMPT 129, 2017

55. Precedence of operators in C++
( ) [] . innermost first
(pre) + - ! ~ (unary operators)
* / %
+ -
= += -= *= /= %=
Evaluate 2 right to left
Evaluate 1, 3, 4 and 5 left to right
© Janice Regan, CMPT 129, 2017

56. Integer expressions Let A=12 B=15 C=3 D=5 E=2 B/D 3 A/D 2 C%E 1 A%D 2
(A + (B – E) * A) % E + C*E 6
© Janice Regan, CMPT 129, 2017

57. Float Expressions Let A=12.2 B=15.7 C=3.0 D=5.1 E=2.5 B/D 3.078431
A/D
(A + B / C)
(A + B) / C * D
(A + (B – E) * A) / E + C*E
A*A + C*C
© Janice Regan, CMPT 129, 2017

58. Assignment Statements
Form: result = expression;
Example: A = B + C * D;
NOT the same as an = in an equation
Each variable is associated with a location in memory
Evaluate the expression on the right (B+C*D)
Multiply the value in the memory location associated with variable C by the value in the memory location associated with variable D
Add the product to the value of the in the memory location associated with variable B
The value of the expression on the right hand side is placed in the memory location associated with variable A
© Janice Regan, CMPT 129, 2017

59. Why use increment / decrement
Q = (++A + B / --C);
This is a shorthand way of writing
C = C – 1;
A = A + 1;
Q = (A + B / C);
© Janice Regan, CMPT 129, 2017

60. Why use increment / decrement
Q = (A-- + B / --C);
This is a shorthand way of writing
C = C – 1;
Q = (A + B / C);
A = A - 1;
© Janice Regan, CMPT 129, 2017

61. Assignment operators
A = B assign value of expression B to variable A, store value of expression B in A
A += B add the value of expression B to the value of variable A, store result in A
A -= B subtract the value of expression B from the value of variable A, store result in A
A *= B multiply the value of variable A by the value of expression B, store result in A
A /= B divide the value of variable A by the value of expression B, store result in A
© Janice Regan, CMPT 129, 2017

62. Assignment Statements:
Form: result = expression;
Example: X = X * Y;
Each variable is associated with a location in memory
Evaluate the expression on the left (X*Y)
Multiply the value in the memory location associated with variable X by the value in the memory location associated with variable Y
The product is the value of the expression
The product is placed in the memory location associated with variable X overwriting the previous value of X
© Janice Regan, CMPT 129, 2017