Lab #2.md

Programming 2 - Lab #2

By TA Ahmed Arafat (Ahmed Mohamed Yousry)

Topics To Be Discussed:

1. Case-Sensitivity in C++

2. Printing on Screen (Cout)

3. Taking An Input (Cin)

4. Arithmetic Operators (+ - * / %)

5. Assignment Operators (+= -= *= /= %=)

6. Increment Operators (Postfix & Prefix ++ --)

7. Conditions (if/else/else if)

8. Comparison Operators ( == != > < >= <=)

9. Logical operators (&& || !)

10. Switch Statement

program 1: Grade GPA (if statement)

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1. Case-Sensitivity in C++

• Case-Sensitivity : Means that writing in upper case is different from writing in lower case
• For Example, if I write the following code:

#include <bits/stdc++.h>
using namespace std;

int main()
{
    INT x;
}

This will generate a compilation error (error in the syntax) as you typed INT not int
so Keywords *: like for/while/int/using/namesapce/do/if/else/break/continue/switch/class and so on should be named in lowercase not upper one

• Again, *Keywords: is a predefined or reserved word in C++ library with a fixed meaning and used to perform an internal operation. C++ Language supports more than 64 keywords.

• This means that C++ programming language is case-sensitive (java is also a case-sensitive)

• Languages like HTML (markup language not a programming one) & SQL (used for Databases) are case-insensitive languages, you can write in SQL both words SELECT/select

• Also note the following

#include <bits/stdc++.h>
using namespace std;

int main()
{
    int x;
    int X;
}

This code will run perfectly as I have named two variables one x & X, one is uppercase and the other is lowercase

2. Printing on Screen (Cout)

• The syntax of printing a message in the terminal is by using cout
• Let's see the following examples:

int main()
{
    cout<<"Hello World";// print a message
    cout<<"Hello World"<<" My Name Is Ahmed"; // print two messages
    string name = "Ahmed Arafat";
    cout<<"Hello,"<<name;// print a message + value stored in the variable `name`
    cout<<"Hello World\n";// to print `hello` then end the line (the next text will be printed on the next line)
    cout<<"Hello World"<<endl;// another method to end a line using endl
    cout<<"Hello\tAhmed";// `t` stands for tab, the output will be `Hello    Ahmed`
}

Note: 1 tab = 4-8 spaces

3. Taking An Input (Cin)

• Let's observe the following code :

int main()
{
    string name;
    cin>>name;
    cout<<"Hello, "<<name;
}

cin>>name means that the terminal will ask the user to enter a value & this value will be stored in the variable name

4. Arithmetic Operators (+ - * / %)

• Arithmetic operators means mathematical operators
• Let's observe the following code :

int main()
{
  int x1 = 10 + 2;//12
  int x2 = 10 - 2;//8
  int x3 = 10 * 2;//20
  int x4 = 10 / 2;//5
  int x5 = 10 % 2;//0
}

Note: for Arithmetic operators the must be an operator (+ - * / %) & two operand (numbers)
So we type 2 + 2 we cannot say 2 + only or + 2 (means that it is a positive number) we must have two numbers (operand)

• Let's take about the operator % which is called reminder or Modulo
• It produces the remainder of an integer division
• Let's observe the following expression 10 % 2, the output will be ZERO, why because we subtract the value on the right side of % from the value on the left side of %, let's see. First we subtract 2 from 8, the result will be 6 then again subtract 2 then the result will be 4, continue this process 10-8-6-4-2-0. NOTE : once the number of the left become less than the number of the right 0 % 2 the result will be the number on the left (which is 0)
• Can we say that we want to subtract 2 from 0, or 100 from 5, its meaningless so that the number on the left side will be the result
• Another important note: let's say that 1234 % 5 and the 5 is the n. In this case the result will be from 0 to 4
• The result will be and MUST be from 0 to n-1, so the result will be one of the following values (0,1,2,3,4)

5. Assignment Operators (+= -= *= /= %=)

• Let's observe the following code :

int main()
{
    int x = 10;
    // The compiler will convert the following lint to
    // x = x + 2  , and so on for the rest
    x += 2;//x will be 12
    // x = x - 2 
    x -= 2;//x will be again 10
    // x = x * 2 
    x *= 2;//x will be 20
    // x = x / 2 
    x /= 2;//x will be again 10
    // x = x % 2 
    x %= 2;//x will be again 0
}

6. Increment Operators (Postfix & Prefix ++ --)

• Postfix means x++ or x-- (whether it is increment or decrement)

Post word means after (like saying post-war)

• Prefix means ++x or --x (whether it is increment or decrement)

Pre word means before (like saying prepaid)

7. Conditions (if/else/else if)

8. Comparison Operators ( == != > < >= <=)

9. Logical operators (&& || !)

10. Switch Statement

#include <iostream>
using namespace std;

int main()
{
    int grade;
    string res;
    cin>>grade;
    if(grade >= 90) res = "A+";
    else if(grade >= 85) res = "A";
    else if(grade >= 75) res = "B+";
    else if(grade >= 70) res = "B";
    else if(grade >= 60) res = "C+";
    else if(grade >= 55) res = "C";
    else if(grade >= 50) res = "D";
    else res = "F";

    cout<<"Your Result Is: "<<res;

}

program 2: check drink (switch)

program 4: sum input from users if n != -1 (while)

program 5: sum of numbers from 1 to N (for loop)

program 6: https://codeforces.com/group/ctwVty4ZXZ/contest/267232/problem/Q