Debugging Tips - What is bug and debugging?

Key Takeaways

hello and welcome to core basics coding tutorial in today's session we are going to learn what is bug and what is debugging first let's see what is bug when it comes to software programming or writing code bug means you wrote a program or a piece of score that doesn't behave the way you expected meaning the program has some kind of fault or error this is called program having a bug for example take a look at this example here you are taking two numbers as an input and you are just doing sum of these two numbers and printing it now this program is written in Python using py charm editor but really the concept applies to any program it could be in C++ Java or any programming language right so if I run this program here it will first ask me to enter two number so I enter two and three and it is saying sum is 23 now if you just look at the program what it is doing is it is adding two numbers n1 n2 and in this function all I am doing is a plus B I am returning that and that's what we are printing here so if you just read the program it everything looks okay so you will wonder what's wrong with this right so this means this program has a bug it doesn't behave the way you expect it to behave so the process of finding bug and fixing it is called debugging debug means debug meaning you are removing bugs from your program this is similar to fixing problem with let's say your car you are driving your car and car has problem and it's not working or it is making some weird sound you will take it to a mechanic and in the garage the mechanic will open the car he will examine different parts and do different tests and he will figure out what is wrong similarly this programming not behaving well so I have to to kind of dig into it analyze the step of execution and watch all the variables and all kind of programming states that are corresponding to that execution and then eventually figure out what's going wrong another real-life example of debugging is called let's say you are sick you go to the doctor and doctor will ask you to do a blood test so they will take your blood sample and the blood sample will go to a laboratory in the laboratory the technician will examine the blood under Microsoft microscope he will do various tests and he will figure out whether you have a sugar level problem or cholesterol problem etc so debugging is similar it's basically using a debugger you are trying to find a problem or within a program that is not behaving well ok so let's examine this program and find out why it is not behaving the way you expect it to behave now right now I am using py charm editor or you can use microsoft visual studio or eclipse whatever editor you're familiar with these are each a circle also called IDE meanings integrated development environment which allows you to write the code as well as debug it ok so here in py charm I will click on this icon you see there is a bug icon here so this means I'm debugging it now before I do bug it um I have set a breakpoint here see normally what happens is if you don't click on this bug and if you directly run the program it will ask you for input and it was straight of executed right so it will just pass through this line and you will not find a chance to examine the state of program carefully so what you want to say program is you want to say ok when you come here at this point so these two things are fine you are just taking input right so I want to I want program to stop here so this means break so this red circle when I click here or when I press f9 in many of the editors f9 is a shortcut for setting a breakpoint breakpoint means when program reaches here it will stop it will not go further so let me click on bug icon here and see what happens okay now here as you can see the program wait a minute yes so the programmed R is asking me to enter first number so 2 and then at ur enter 3 ok I have to use their - concept here like step over and step into meaning go to the next line or go inside the function I want to go inside this add number function and see what's going on so you use this option f11 or step in - when you do that it goes inside the add number function now here one thing you notice is a and B are in course meaning their strings okay also if you go here let me find out the variable ok I'm going to move this back to the down because that's more convenient ok so if you look at the span here here it says variable a and B so this panel is variables panel it shows all the local variables in your function and 2 & 3 are strings actually now when I say next you see s is 23 because what it is doing is it is just adding two strings together right so that's what the problem is the problem is that you are adding two strings instead of adding two numbers so now what you need to do is so I'll so now I know what is the problem the problem is we are not adding two numbers we are adding two strings okay so when you say next nature later spin printing as 23 okay cool so that's why you got the output of 23 here okay so what I need to do is I need to convert these two numbers into integer so when I took it from the console it they were strings when I do N 1 is equal to int and 1 what it is doing is converting a string into integer then n 2 is equal to int n 2 okay so now so let me again set up a breakpoint here and see what happens when I D bug it once I can is asking for the number 2 so when I enter 2 and 1 you can see here it is straight still a string okay until this point N 1 now good thing about pH I'm debugger is in the comment section it will show you the value of that variable when I go to next now see you see that those quotes are gone now so now this became a true number okay now it is asking me for the second number so now second number is also string because there is a quote here when I say next it becomes 3 because of this line okay integer now when I go inside the function a and B as you can see here are integer numbers and when I say next now s is 5 so when I run it now the sum is 5 so now it's behaving the way I expect it to behave so I just found a bug in the code and fixed it ok that was all about what is bug and debugging thank you very much for watch