terms: flooding network propagation
--- cpp
statement - type of instruction that causes the program to perform some action.
function - a collection of statements that execute sequentially
Declaration statements
Jump statements
Expression statements
Compound statements
Selection statements (conditionals)
Iteration statements (loops)
Try blocks
####################
Rule
Every C++ program must have a special function named main (all lower case letters). When the program is run, the statements inside of main are executed in sequential order.
####################
preprocessor directive
#include <iostream>
{
function body
}
// single line comments
/* multiple line comments */
data is any information that can be moved, processed, or stored by a computer.
value - a single piece of data stored somewhere
In C++, direct memory access is not allowed. Instead, we access memory indirectly through an object.
An object is a region of storage (usually memory) that has a value and other associated properties
A named object is called a variable, and the name of the object is called an identifier.
runtime - when the program is run
instantiation - object is created and assigned a memory address
variable - a named region of memory
identifier - name that a variable is accessed by
type - tells the program how to interpret a value in memory.
copy assignment / assignement = after a variable has been defined, you can give it a value
= assignment operator
initialization - variable defined and provided an initial value
initializer - the value used to initialize a variable
4 ways to initialize
int a; // no initializer
int b = 5; // initializer after equals sign - copy initialization
int c( 6 ); // initializer in parenthesis - direct initialization
int d { 7 }; // initializer in braces
copy initialization - when initializer follows an equal sign
direct initialization
brace initialization/uniform initialization/list initialization
3 kinds of brace initialization
- int width { 5 }; // direct brace initialization of value 5 into variable width (preferred)
- int height = { 6 }; // copy brace initialization of value 6 into variable height
- int depth {}; // value initialization (see next section
value initialization and zero initialization
- variable initialized with empty braces
- value assigned is 0
- zero initialization
Initialization gives a variable an initial value at the point when it is created. Assignment gives a variable a value at some point after the variable is created.
Direct brace initialization.
<< - insertion operator - cout
>> - extraction operator - cin
using namespace std; - "using directive" avoid
std::endl vs ‘\n’
######
Best practice
Prefer ‘\n’ over std::endl when outputting text to the console.
######
_____1.6
- initialization - object given value at the point of definition
- assignment - object given value beyond the point of definition
- uninitialized - object not given a known value yet
always initialize your variables
Undefined behavior - executing code whose behavior not well defined in c++
_____1.7
keywords - 92 words reserved by c++ for
identifiers - override, final, import, and module.
ide changes color to blue of these words
c++ is case sensitive
always start lowercase
not number
no symbols
no space
no reserved words
snake_case
camelCase or interCapped
######
Best practice
When working in an existing program, use the conventions of that program (even if they don’t conform to modern best practices). Use modern best practices when you’re writing new programs.
######
_ underscores - OS, library, and/or compiler use
correct (follows convention)
incorrect (does not follow convention)
invalid (will not compile)
_____1.8 Whitespace
_____1.9 Literals and operators
literals or literal constant - fixed values inserted into source code
arity, the number of operatands an operator takes as input
- unary
- binary
- tertiary
_____1.10 Expressions
Expression
An expression is a combination of literals, variables, operators, and function calls that can be executed to produce a singular value.
Evaluation
The process of executing an expression is called evaluation,
Result
and the single value produced is called the result of the expression.
_____2.1
function = reusable sequence of statements to do a job
user-defined function = function that user writes himself
function call = an expression that tells the CPU to interrupt the current function and execute another function
caller = the function that initiated the function call
callee or called function = the function being called
### syntax to define a user defined function
return-type identifier() // identifier replaced with the name of your function
{
// Your code here
}
the curly braces identify the function body
###
metasyntactic variable - placeholder names
_____2.2
return value
return type
return statement
return value
""""""
When you write a user-defined function, you get to determine whether your function will return a value back to the caller or not. To return a value back to the caller, two things are needed.
First, your function has to indicate what type of value will be returned. This is done by setting the function’s return type, which is the type that is defined before the function’s name. In the example above, function getValueFromUser has a return type of void, and function main has a return type of int. Note that this doesn’t determine what specific value is returned -- only the type of the value.
Second, inside the function that will return a value, we use a return statement to indicate the specific value being returned to the caller. The specific value returned from a function is called the return value. When the return statement is executed, the return value is copied from the function back to the caller. This process is called return by value.""""""
status code
exit code
return code
DRY = Don't Repeat Yourself
_____2.3 Function parameters and arguments
function parameter - is a variable used in a function.
A function parameter is a variable used in a function. Function parameters work almost identically to variables defined inside the function, but with one difference: they are always initialized with a value provided by the caller of the function.
argument - value that is passed from the caller to the function when a function call is made
pass by value - parameters of the function created as variables, value is copied
//This is a hard topic, learn more about passing of value
**function prototyping
_____2.4 Local scope
Function parameters, as well as variables defined inside the function body, are called local variables (as opposed to global variables, which we’ll discuss in a future chapter).
An identifier’s scope determines where the identifier can be accessed within the source code. When an identifier can be accessed, we say it is in scope. When an identifier can not be accessed, we say it is out of scope.
_____2.5 Why functions are useful and how to use them effectively
- organization
- reusability
- testing
- extensibility
- abstraction
refactoring - when a function is split into multiple sub-functions
_____2.6 forward declarations
A forward declaration allows us to tell the compiler about the existence of an identifier before actually defining the identifier.
function prototyping - a declaration statement. Is composed of
- return type
- name
- parameters
#### ODR #####
One Definition Rule
1. Within a given file, a function, object, type, or template can only have one definition.
2. Within a given program, an object or normal function can only have one definition. This distinction is made because programs can have more than one file (we’ll cover this in the next lesson).
3. Types, templates, inline functions, and variables are allowed to have identical definitions in different files.
Declaration - a statement that tells the compiler about the existence of an identifier and its type information.
in C++ - all definitions are also declarations
but not all declarations are definitions
Pure declarations - "An example of this is the function prototype -- it satisfies the compiler, but not the linker. These declarations that aren’t definitions are called pure declarations. Other types of pure declarations include forward declarations for variables and type declarations (you will encounter these in future lessons, no need to worry about them now)."
Function prototype - A function prototype is a declaration statement that includes a function’s name, return type, and parameters. It does not include the function body.
Forward declaration - A forward declaration tells the compiler that an identifier exists before it is actually defined.
- according to Bucky this is actually called "Function prototyping"
Notes:
Compiler fails to compile if function does not have the same number of parameters.
Other compiler link problems - if a function is undefined (no body), linker can't resolve the function call.
Violating ODR rule 2 - "Within a given program, an object or normal function can only have one definition"
_____2.8 naming collisions and namespaces
:: in std::cout - scope resolution operator
The identifier to the left of the :: symbol identifies the namespace that the name to the right of the :: symbol is contained within. If no identifier to the left of the :: symbol is provided, the global namespace is assumed.
using directive - (using namespace std) - tells the compiler to check a specified namespace when trying to resolve an identifier that has no namespace prefix
_____2.9 introduction to the pre-processor
Prior to compilation, program goes through translation.
Translation has many phases.
Preprocessor directive (or simply directive) scans from top to bottom of file. Start with # and end with a new line.
Macro defines
a macro is a rule that defines how input text is converted into replacement output text.
object-like macros
function-like macros
Object-like macros can be defined in one of two ways:
#define identifier
#define identifier substitution_text
When the preprocessor encounters this directive, any further occurrence of the identifier is replaced by substitution_text. The identifier is traditionally typed in all capital letters, using underscores to represent spaces.
No comments:
Post a Comment