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In this video, you will learn about conditions and branching.

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Comparison operations compares some value or operand.

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Then based on some condition,

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they produce a Boolean.

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Let's say we assign a value of a to six.

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We can use the equality operator denoted with

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two equal signs to determine if two values are equal.

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In this case, if seven is equal to six.

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In this case, as six is not equal to seven,

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the result is false.

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If we performed an equality test for the value six,

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the two values would be equal.

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As a result, we would get a true.

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Consider the following equality comparison operator:

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If the value of the left operand, in this case,

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the variable i is greater than the value of the right operand,

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in this case five,

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the condition becomes true or else we get a false.

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Let's display some values for i on the left.

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Let's see the value is greater than five in green and the rest in red.

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If we set i equal to six,

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we see that six is larger than five and as a result, we get a true.

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We can also apply the same operations to floats.

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If we modify the operator as follows,

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if the left operand i is greater than or equal to the value of the right operand,

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in this case five,

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then the condition becomes true.

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In this case, we include the value of

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five in the number line and the color changes to green accordingly.

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If we set the value of i equal to five,

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the operand will produce a true.

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If we set the value of i to two,

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we would get a false because two is less than five.

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We can change the inequality if the value of the left operand, in this case,

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i is less than the value of the right operand,

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in this case, six.

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Then condition becomes true.

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Again, we can represent this with a colored number line.

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The areas where the inequality is true are marked in

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green and red where the inequality is false.

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If the value for i is set to two,

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the result is a true.

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As two is less than six.

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The inequality test uses an explanation mark preceding the equal sign.

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If two operands are not equal,

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then the condition becomes true.

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We can use a number line.

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When the condition is true,

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the corresponding numbers are marked in green and red for where the condition is false.

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If we set i equal to two,

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the operator is true as two is not equal to six.

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We compare strings as well.

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Comparing ACDC and Michael Jackson using the equality test,

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we get a false, as the strings are not the same.

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Using the inequality test,

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we get a true, as the strings are different.

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See the Lapps for more examples.

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Branching allows us to run different statements for a different input.

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It's helpful to think of an if statement as a locked room.

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If this statement is true,

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you can enter the room and your program can run some predefined task.

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If the statement is false,

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your program will skip the task.

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For example, consider the blue rectangle representing an ACDC concert.

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If the individual is 18 or older,

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they can enter the ACDC concert.

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If they are under the age of 18,

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they cannot enter the concert.

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Individual proceeds to the concert their age is 17,

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therefore, they are not granted access to the concert and they must move on.

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If the individual is 19,

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the condition is true.

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They can enter the concert then they can move on.

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This is the syntax of the if statement from our previous example.

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We have the if statement.

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We have the expression that can be true or false.

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The brackets are not necessary. We have a colon.

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Within an indent, we have the expression that is run if the condition is true.

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The statements after the if statement will run

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regardless if the condition is true or false.

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For the case where the age is 17,

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we set the value of the variable age to 17.

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We check the if statement,

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the statement is false.

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Therefore the program will not execute the statement to print, "you will enter".

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In this case, it will just print "move on".

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For the case where the age is 19,

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we set the value of the variable age to 19.

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We check the if statement.

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The statement is true.

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Therefore, the program will execute the statement to print "you will enter".

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Then it will just print "move on".

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The else statement will run a different block of code if the same condition is false.

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Let's use the ACDC concert analogy again.

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If the user is 17,

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they cannot go to the ACDC concert but they

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can go to the Meat Loaf concert represented by the purple square.

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If the individual is 19,

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the condition is true,

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they can enter the ACDC concert then they can move on as before.

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The syntax of the else statement is similar.

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We simply append the statement else.

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We then add the expression we would like to execute with an indent.

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For the case where the age is 17,

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we set the value of the variable age to 17.

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We check the if statement,

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the statement is false.

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Therefore, we progress to the else statement.

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We run the statement in the indent.

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This corresponds to the individual attending the Meat Loaf concert.

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The program will then continue running.

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For the case where the age is 19,

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we set the value of the variable age to 19.

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We check the if statement,

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the statement is true.

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Therefore, the program will execute the statement to print "you will enter".

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The program skips the expressions in

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the else statement and continues to run the rest of the expressions.

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The elif statement, short for else if,

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allows us to check additional conditions if the preceding condition is false.

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If the condition is true,

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the alternate expressions will be run.

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Consider the concert example,

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if the individual is 18,

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they will go to the Pink Floyd concert instead of

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attending the ACDC or Meat Loaf concerts.

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The person of 18 years of age enters the area as they are not over 19 years of age.

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They cannot see ACDC but as their 18 years,

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they attend Pink Floyd.

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After seeing Pink Floyd, they move on.

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The syntax of the elif statement is similar.

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We simply add the statement elif with the condition.

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We, then add the expression we would like to

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execute if the statement is true with an indent.

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Let's illustrate the code on the left.

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An 18 year old enters.

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They are not older than 18 years of age.

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Therefore, the condition is false.

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So the condition of the elif statement is checked.

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The condition is true.

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So then we would print "go see Pink Floyd".

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Then we would move on as before.

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If the variable age was 17,

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the statement "go see Meat Loaf" would print.

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Similarly, if the age was greater than 18,

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the statement "you can enter" would print.

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Check the Lapps for more examples.

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Now let's take a look at logic operators.

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Logic operations take Boolean values and produce different Boolean values.

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The first operation is the not operator.

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If the input is true,

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the result is a false.

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Similarly, if the input is false,

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the result is a true.

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Let A and B represent Boolean variables.

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The OR operator takes in the two values and produces a new Boolean value.

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We can use this table to represent the different values.

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The first column represents the possible values of A.

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The second column represents the possible values of B.

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The final column represents the result of applying the OR operation.

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We see the OR operator only produces a false if all the Boolean values are false.

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The following lines of code will print out: "This album was made in the 70s' or 90's",

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if the variable album year does not fall in the 80s.

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Let's see what happens when we set the album year to 1990.

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The colored number line is green when the condition is

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true and red when the condition is false.

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In this case, the condition is false.

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Examining the second condition,

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we see that 1990 is greater than 1989.

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So the condition is true.

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We can verify by examining the corresponding second number line.

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In the final number line,

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the green region indicates, where the area is true.

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This region corresponds to where at least one statement is true.

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We see that 1990 falls in the area.

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Therefore, we execute the statement.

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Let A and B represent Boolean variables.

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The AND operator takes in the two values and produces a new Boolean value.

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We can use this table to represent the different values.

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The first column represents the possible values of A.

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The second column represents the possible values of B.

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The final column represents the result of applying the AND operation.

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We see the OR operator only produces a true if all the Boolean values are true.

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The following lines of code will print out "This album was made in the

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80's" if the variable album year is between 1980 and 1989.

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Let's see what happens when we set the album year to 1983.

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As before, we can use the colored number line to examine where the condition is true.

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In this case, 1983 is larger than 1980,

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so the condition is true.

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Examining the second condition,

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we see that 1990 is greater than 1983.

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So, this condition is also true.

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We can verify by examining the corresponding second number line.

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In the final number line,

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the green region indicates where the area is true.

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Similarly, this region corresponds to where both statements are true.

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We see that 1983 falls in the area.

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Therefore, we execute the statement.

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Branching allows us to run different statements for different inputs.

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(Music)