1. COP 3330 Object-oriented Programming in C++
(Extremely incomplete) Review of C++ Fundamentals
Spring 2019

2. From a C++ Program to an Executable
Create source code containing the program
*.h (*.hpp), *.cpp (*.cc)
Run preprocessor to convert source file directives to source code program statements
#include, #ifndef, #define, #endif, #pragma ……
Compile source code into machine instructions
Link hardware-specific code to produce an executable
If errors or bugs detected, go to step 1
g++ or
make

3. From a C++ Program to an Executable

4. Primitive Types and Operators
Basic Types
(unsigned) int, char, float, double, ……
string (C++ STL): #include <string>
auto (C++ 11): tells the complier to determine variable’s type from the initialization value:
auto amount = 100; (int)
Basic Operators
Arithmetic: +, -, *, /, %, ++;
= and ==
Pointer operations: *, &
Comparisons: <, <=, >, ……
Streams: << and >>

5. Input, Processing and Output
Three steps that a program typically performs
Gather the data
From keyboard: cin, ……
From files (on hard drives): open, read, eof, close …
Process the input data using algorithms
Display results as output
Send it to the screen: cout, ……
Write to files: open, write, close

6. Type Casting Used for manual data type conversion C-style cast
cout << ch << “ is ” << (int) ch;
Prestand C++ cast: value in ();
cout << ch << “ is ” << int(ch);
Static_cast (preferred)
cout << ch << “ is ” << static_cast<int>(ch);

7. If-else Statement Short-circuit Evaluation
If(I have one more day till deadline)
watch_Youtube();
write_my_C++_code();
If(I plan to fail COP 3330)
watch_Youtube();
else
write_my_C++_code();
Short-circuit Evaluation
if(expression1 && expression2)
expression1 is FALSE, so …
if(expression1 || expression2)
expression1 is TRUE, so …
Applies to all the Boolean expressions!

8. Check Numeric Ranges
Used to test to see if a value falls inside a range:
if (grade >= 0 && grade <= 100)
cout << "Valid grade";
Can also test to see if value falls outside of range:
if (grade <= 0 || grade >= 100)
cout << "Invalid grade";
Cannot use mathematical notation:
if (0 <= grade <= 100) //doesn’t work!
Not equal:
if (grade != 100)

9. Flags Variables that signals a condition
Usually implemented as a bool variable
In practice, can be used extremely effectively
Example: linear search

10. Prefix vs. Postfix
++ and -- operators can be used in complex statements and expressions
In prefix mode (++val, --val) the operator increments or decrements, then returns the value of the variable
In postfix mode (val++, val--) the operator returns the value of the variable, then increments or decrements
int num, val = 12;
cout << val++; // displays 12, val is now 13;
cout << ++val; // sets val to 14, then displays it
num = --val; // sets val to 13, stores 13 in num
num = val--; // stores 13 in num, sets val to 12

11. For Loop for(initialization; test; update)
statement; // or block in { }
Perform initialization
Evaluate test expression
If true, execute statement
If false, terminate loop execution
Execute update, then re-evaluate test expression

12. Which Loop to Use? The while loop is a conditional pretest loop
Iterates as long as a certain condition exits
Example: validating input
Example: Reading lists of data terminated by a sentinel
The do-while loop is a conditional posttest loop
Always iterates at least once
Example: Repeating a menu
The for loop is a pretest loop
Built-in expressions for initializing, testing, and updating
Situations where the exact number of iterations is known

13. Let’s Change the Loop Behavior
Break
Terminate execution of a loop
When in an inner loop, terminates that loop and goes back to outer loop
Continue
Go to end of loop and prepare for next repetition
while, do-while loops: go to test, repeat loop if test passes
for loop: perform update step, then test, then repeat loop if test passes
Return
Go out of the function, no matter how deep I am in a nested loop

14. Function Definition Definition includes:
return type: data type of the value that function returns to the part of the program that called it
name: name of the function.
parameter list: variables containing values passed to the function
body: statements that perform the function’s task, enclosed in {}

15. Passing Data to Functions
Pass by value: when an argument is passed to a function, its value is copied into the parameter
Changes to the parameter in the function DO NOT affect the value of the argument
Pass by reference: changes to a reference variable are made to the variable it refers to!
A reference variable is an alias for another variable, defined with an ampersand (&)
A mechanism that allows a function to work with the original argument from the function call, NOT a copy of the argument
Provides a way for the function to ‘return’ more than one value
Pass by pointer: C style, obsolete

16. Arrays Variable that store multiple values of the same type
Values are stored in adjacent memory locations
Declared using [] operator:
int tests[5];
Each element in an array is assigned a unique subscript
Subscripts start at 0 !
No bounds checking for invalid subscripts!
Arrays must be accessed via individual elements:
cout << tests; // not legal
Don’t try to assign one array to the other:
newTests = tests; // Won't work

17. Vector (Almost Always a Better Solution)
Vector in Standard Template Library (STL)
#include <vector>
vector<int> scores;
vector<int> scores(30); //initial size 30
vector<int> scores(30,0); //initialize to 0
scores.push_back(95);
size_t vec_size = scores.size();
Automatically adds space as more is needed – no need to determine size at definition

18. Pointer Using a memory address to work with a piece of data
int *intptr = nullptr; // C++11
intptr = &num;
if (ptr1 == ptr2) // compares addresses
if (*ptr1 == *ptr2) // compares contents
Constant pointer
A constant pointer is a pointer initialized with an address, and cannot point to anything else int value = 22; int * const ptr = &value;
num
intptr 25
0x4a00

19. Const Pointer vs. Pointer to Const

20. Dynamic Memory Allocation
Uses new operator to allocate memory
double *dptr = nullptr;
dptr = new double;
new returns address of memory location
Use delete to free dynamic memory:
delete dptr;
Use [] to free dynamic array:
delete [] arrayptr;
Only use delete with dynamic memory!

21. Questions