Lecture 2: C++ Basics Flashcards
To use functions and objects in libraries, we must
Include them in our code and by doing this with an include directive at the top of our file.
Ex:
#include <iostream></iostream>
A namespace is
A collection of names (such as cin and cout)
An object named cout exists in the std (or standard) namespace. It might also exist in other namespaces, we instruct C++ to use the
Cout from the std namespace. Example of:
using namespace std;
When runs a program, executions always begins at the
Main function
The return 0 at the end of our main function tells to
End the program here
Ex:
cout «_space;“Hello World”;
return 0;
Use a comment to write something in the program that the compiler will
Ignore
We can also place a comment on the same line as a statement. This is referred to as an
Incline comment
To create a multi-line comment, we can also use the following technique:
/Print “Hellow World” to the screen
These lines are ignored by the compiler
End of comment /
A variable can hold data of
A specific type and for now, we will only use variables that hold numbers
When we declare a variable, we tells to set aside a location in
Main memory large enough to hold a value of the given type
The declaration statement tells to:
1) Set aside a location in memory large enough to hold an integer
2) Given that memory location the name
Can place a value in or retrieve a value from a variable’s memory location by using its
Name
This code declares three variables. When they are created, they are each assigned a different
Memory address
The addresses assigned might be different each time the program runs. It depends on
What memory is free at the moment
Only need to use a variable’s name to access its
Memory address
The name of a variable is also called an
Identifier
Each identifier’s name must be unique in its
Scope (more on scope later) and the program only have one scope, so all identifier must be unique
C++ is a
Case sensitive language and this means the difference between uppercase and lowercase letters matters
A keyword or reserved word is
A special type of identifier
Ex: int, double, void, bool, for, while
Naming conventions - if a variable name is one word, it is written in lowercase
Ex: int number;
If a variable name has more than one word, it is written in
Camelcase
Ex: int numberOfBars
Since an identifier cannot have spaces, all words must be combined into
One word
Assignment statement
Ex: totalWeight = 5;
An assignment statement uses the “ = “ operator, also known as the
Assignment operator
Unlike in math, “ = “ does not assert that its left and right operands are
Equal, rather it takes the value on the right and assigns it to a variable on the left
An expression is a series of
Values and operators that evaluates to a single value
When an expression is the right operand of “ = “, it is
Evaluated first
When a variable appears to the LEFT of “ = “, we are referring to its
Memory location
When a variable appears to the LEFT of “ = “, we are referring to
The value stored at its memory location
An uninitialized variable has
Garbage data
To avoid uninitialized variables, we can give them a value on the same line that we
Declare them
Ex: int miniNumber = 3;
An input stream is a stream of
Input being entered into the computer for our program to use
The programs as we write this course will receive this input comes from
The keyboard
An output stream is a stream of
Output generated by our program and given to the user
The program we write in this course will display their output in
A console window on the user’s monitor
cout «_space;””; is used to
Display information to the screen
Recall that to use it, we must include, what?
iostream in our program
cout «_space;””; is short for
Console output
«_space;is called the
Arrow symbol or stream insertion operator
«, the stream insertion oeprator sends the value of
its right operand to its left operand (cout) then cout will print the value to the screen
You can think of «_space;as an arrow pointing the data to be printed to
Cout
Escape sequence
The backslash and the following character are referred to when a backflash appears before a character in a string, we are telling the compiler to not actually include that letter in the string
Using “cin” for input is similar to using
Cout for output
Two arrows pointing to the right are the
Extraction operator “»”
“cin” receives keyboard input from the user and places it in a
Pre-declared variable
Note: It must be declared but does not need to be
Initialized
Ex:
int number; // ‘number is correctly pre-declared’
cin»_space; number;
When an extraction operator statement is
Reached, program execution pauses
Since program execution pauses when an extraction operator is
Reached, it is important to always display a prompt before reading input to cin
A prompt is text asking the user to
Enter input (and telling them what that input should be)
It is possible to retrieve values for more than one variable with
A single “cin” statement
Ex:
int price, amount;
cout «_space;“Enter the price and amount: “;
cin»_space; price»_space; amount;
Keyboard buffer
The character and the user types are stored in a section of memory
include <string> and note that we also need to add</string>
using namespace std if we have not already
Once the string library is included in our program, we can declare variable of type string as we would
Any other data type
Ex:
string day;
day = “Monday”;
The right operand of the assignment operator is a
String literal
A string literal is
Text placed inside quotation marks
It is called literal because
It is not a variable value. Rather the letters inside the quotes are the literal string being assigned to the left operand.
The “+” operator performs a different operation if its two operands are
String rather than numeric values are known “string concatenation”
As with numeric and character values, it is possible to use the»_space; operator with
“cin” to input a “string” from the keyboard
“cin” ignores leading whitespace characters, so it is
Continue reading from the buffer
When “cin” reaches the first non-leading whitespace character in the buffer, it stops
Reading and sends the characters that have been read to name
Everything that has been read is cleared from
The buffer
When this statement is reached, the keyboard buffer is
Not empty and executions does not pause and cin reads the first character in the buffer
