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Welcome to this lecture about for loops.

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Before starting.

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We need to explain what is a loop a loop is a block of code that iterate a list of commands as long

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as the loop control condition is true so how it looks like here is the standard for loop.

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It takes first item from the list and assign its value to variable arc.

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Then a list of commands between the keyboard to do and done are executed and after this one loop is

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finished.

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Into variable Eric is assigned next item from the list and so on to understand it fully.

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We can look at this example.

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We are iterating through a list which contains three items.

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Mercury Venus and act.

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Firstly to variable planet is assigned variable Mercury.

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Then we will perform commands between keyboards due and done which in our case means printing value

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of variable planet which is now Mercury then into variable planet is assigned to Venus and we will print

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it also.

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And then finally available act is assigned into variable planet and Venus printed.

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There are no other items to loop over so the loop control condition is false and we are continuing with

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the script code after a keyboard.

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Done very often you can see looping over a value of a variable.

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Here you can see we have assigned into two variable plummets string.

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Mercury Venus at what will be the result if we loop over it.

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Result will be the same as in previous slide.

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So the question is why why the for loop prints each planet instead of printing just one thing.

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Because internal field separator definitely separate by space for loop doesn't see only one string thanks

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to internal field separator it sees space strings.

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Mercury Venus and act but if we in our example used quotation marks with the variable planets we would

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basically tell strictly follow created string planet and don't separate for that case.

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The for loop would iterate only one time and we would see printed Mercury Venus act as a one string

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on one line Well let's see another example with internal field separator into variable planets.

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We are assigning Mercury Venus ahead separated by comma for a loop.

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In that case would iterate only one time and we would see printed only one string as internal field

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separator doesn't contain comma symbol.

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There is nothing to separate in our variable s internal field separator default separates.

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Also by New Line we can assign into variable planets Mercury Venus and separated by New Line.

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And in that case would internal field separator separate it our string to three strings and as output

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of four loops we would see printed each planet on different line.

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We can in four loops also use wildcards.

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Here for example in the list are all text files and for each text file we are printing them using photo

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loops.

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We can integrate any number of times here.

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For example we are iterating through a list of 1 to 10 range.

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So 10 times iterating For loops are also hugely used for looping through all arguments provided as we

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can see in this example.

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We have also possibility to use for loops in C style.

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Here we are using double parenthesis and inside them.

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We are setting default value so we are starting here with variable ie equals to 1.

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Then we have loop control condition so we will iterate through this for loop when the value of variable

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IE is less than or equal to 10 and the last part is incrementing.

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That means at the end of each iteration we are increasing value of variable ie by 1.

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Of course we can also decrement and not only by 1.

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It's up to us of what operation we will do here but most commonly in this type of for loops is spared

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from increment operation by 1.

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So dad was a lot of information in very short time kind of exhausting but don't worry.

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Best way to remember the usage would be to seed on some example in next lecture.