Tech Elevator .Net Week 1 Notes

tech-elevator-week-1.md

Tech Elevator: Week 1 Notes

Command line in Windows is more common than it was

Drives > Folders/Directories > Files

Ways to navigate:

• Absolute = Start from the top

• Relative = start from current folder

• home directory: ~

• this folder: .

• explorer: same as open on mac

• pwd: print working directory

Git Terminology

• Source control: system used to track all the ongoing changes that are made to a codebase
• Git or TFS: (microsoft based version control)
• Repository: houses all of the code and changes
• Clone: downloads a copy of a remote repository to your computer
• Origin: name given to the remote repository
• Stage: identify which files will be committed
• Push: copies changes from local to remote repository
• Pull: fetches updates from a remote repository
• Fork: create a copy of a remote repository
• Upstream: the original (I don't have control over this)
  • My copy is called origin

Terminology

• C#: object oriented programming language
  • Similar to C, C++, Java, Javascript…
  • Compiled into machine level instructions
  • It runs on .Net… Using C# implies that you’re using .Net
• .Net: a framework
  • Provides a way of building applications and includes over 6,000 classes
  • Helps us complete our tasks (e.g. databases, email, security, etc.)
  • I know the task - but I don’t know what class or function to use - so I look it up
  • .Net core & .Net Standard
    • Core works on many platforms - linux, mac. Only new programs - 3 years old.
    • Standard works only on windows and has many more classes
• CLR: common language runtime - something that can process the application
• IDE: Integrated Development Environment - we use Visual Studio
  • Includes ability to troubleshoot, organize, write and run code
  • Visual Studio Community 2017
    • Solution: .sln
      • C# Projects: .csproj
        • C# Files: .cs
          • C# Classes
            • Methods
    • A second project could be a test project - testing the other code we wrote
    • Keyboard Shortcuts
    • Run Program: CTRL + F5
    • Debug Program: F5
      • Step through code execution
  • Intilesense: Autocomplete
• Methods: Functions
• Statement: a unit of code that is executed - carries out an action. Ends in a semicolon ;
• Block: one or more statements of code. Enclosed in curly braces { int x = 3; }
• Scope: code within a block is inside a scope, you can't re-declare variable

{
    int x = 3;
    int x = 4; // error, already declared within this scope
}
{
    int x = 4; // this is fine, they're in different blocks
}

Expressions

• Expression - a statement of code that evaluates to a single result
• Arithmetic expression:

int x = y + 3;
decimal x = 3M;
x += 3; // result: 6M

• Arithmetic operators:
  • + add
  • - subtract
  • * multiply
  • / divide
  • % remainder or mod

32/2   // result: 16
32 % 2 // result: 0
32 % 3 // result: 2

• For the integer operands, the result of a % b is the value produced by a - (a / b) * b
• The sign of the non-zero remainder is the same as that of the first operand, as the following example shows:

Console.WriteLine(5 % 4);   // output: 1
Console.WriteLine(5 % -4);  // output: 1
Console.WriteLine(-5 % 4);  // output: -1
Console.WriteLine(-5 % -4); // output: -1

• Boolean expression
  • true or false
  • x == y;
  • 3 == 4; → false;
• Comparison operators:
  • == equality
  • > greater than (not inclusive)
  • < less than (not inclusive)
  • >= greater than or equal to
  • <= less than or equal to
  • != not equal
• Double: numbers with a decimal point
• Decimal: very precise decimal numbers that you’d use for keeping track of money
• Method: a named block of code. It can accept input values and provides an output value

// `access modifier` `return type` `name`  (`parameters/arguments`)
public int AddTwo (int x, int y)
{
    int sum = x+y;
    return sum;
}

Logical Operators:

• && AND
• || OR
• ! NOT
• ^ XOR (eXclusive OR): a or b but not both

Arrays:

• Arrays: A series of objects of which all items (referred to as elements) are the same type (integers, booleans, etc.)
  • Elements are accessed by Index (your current location)
  • Length: The size of an array. It is fixed and determined when the array is initialized.

// Declare & assign an array:
//  `name` = `type`[`# of elements in array in the correct type`];   
scores = new int[4];

Tells computer to assign space for 4 ints in memory.