 Welcome to this session. It is an introductory session. We already had seen in the preamble that computers are machines, a machine which requires instructions to be given to it. The instructions are given in the form of a program. A computer is expected typically to first read the entire program, understand it and then execute the instructions one by one in the specified order. In this lecture, we will look at some details of how instructions are given and how procedures are written. Of course, we are going to look only at the instructions and procedures meant for human beings. In particular, we will look at the procedure for preparing Indian tea, which is a well known recipe. We will also look at the procedure, which a cashier in the bank uses when he deals with customers may be giving money to them when they come to withdraw money from their account. We often instruct people to do something. For example, we say please get me a glass of water or we say please keep this book on the shelf. Such instructions are verbally given. They are not complex tasks and whatever we say in a simplified manner is very easily understood by someone who we are asking the favour. Please understand that whenever we give such an instruction, the context of that instruction is well understood by both the person who carries out that instruction and by us. For example, when we say keep the book on the shelf, the book is not kept in a shelf which contains clothes or which contains shoes. The person will keep the book on the book shelf. Now that is understood and we understand that that is understood. Such is the way in which simple instructions are given. They are given verbally and they are followed automatically in the correct fashion. However, when a task is complex and the task needs many steps to be carried out, then verbal instructions are often inadequate. More importantly, when we have a complex task that different people have to do at different times at different places in exactly the same way, then obviously we cannot depend upon verbal instruction. This is the situation when we give written instructions. There are many examples of written instructions. Cookbooks or recipes is one example. Instructions at the workplace is another example. Let us look at a recipe for preparing Indian tea. Consider these steps. Take a cup of water in a vessel. Add 2 teaspoons sugar, 1 teaspoon tea leaves and milk. Boil the mixture for 3 minutes. Strain in a tea kettle. Serve in a cup. This is how what we call the Kadak Mithi Chai of India is made. There could be some variations, but generally this is the process that is followed. Please understand that for a person who is not familiar with the Indian tea, such a written procedure is very useful because then exactly the same kind of tea could be prepared by two different people. May be one in China, one in Singapore, one in South America. They all can make tea in this fashion which will be very similar in nature. Consider now the same recipe for preparing Indian tea where the steps are exchanged. Look at these steps. Take a cup of water in a vessel. Boil for 3 minutes. Add 2 teaspoons sugar, 1 teaspoon tea leaves milk. Strain into a tea kettle and serve in a cup. Note that the steps are same as the previous recipe shown in the last slide, except that two steps have been interchanged. The question is, will I get the right kind of Indian tea? So, here is a quiz. If you follow the procedure that was outlined in the last slide, you will serve a good Indian tea, be hot water, see some funny looking mixture or do none of these. One of the reasons why I am giving you this quiz is these are the kind of quizzes that would normally be given to you and you will have to attempt answering them either as a self-practice or as a part of the evaluation. Let us analyze this quiz. Since the water was not boiled with all the ingredients, we will certainly not get good Indian tea. Therefore, A is wrong. The second option B says that we will get hot water. That is not correct because we did add ingredients just before straining. So, some color from the tea leaves will diffuse into the water. Some sweetness of the sugar will diffuse into the water and therefore, we will definitely not get plain hot water. Therefore, B is wrong. Now, because the reasons that I just mentioned, some color from tea leaves and some sweetness from sugar will get added to the water. Therefore, a funny kind of mixture is what will result. C is thus correct. Since C is correct, D is obviously incorrect. We can see that a procedure if not written properly, if the steps are not written in the order in which they need to be executed, then the desired task will not be correctly carried out. Let us now look at a more formal procedure which typically bankers follow. Let us consider an old bank, which still maintains account information in paper form in what is known as lasers. A laser is nothing but a register in which the account information about a customer is maintained. Suppose a customer comes to withdraw some money from the account, the customer will present a check or a withdraw slip. In banking parlance, it is called an instrument. So, any piece of paper or any message which contains information about financial transaction is called an instrument. So, suppose a customer comes and presents a check or a withdraw slip, the customer should be paid cash if balance is adequate and appropriate entries must be made in the laser which maintains account information. Now, this procedure once adopted and used by cashiers can be automatically carried out, but invariably banks will maintain a written procedure. This written procedure is called a job card. Consider this job card for a bank cashier. First step, greet the customer and collect the instrument presented. This is where the check or withdraw slip will be collected by the cashier. Second step, keep the instrument on your right and keep a paper weight on it. Observe the meticulousness that is implied by this instruction. Please note that this instruction is not pertaining to any financial transaction per se, but this is to ensure that the check or withdraw slip given by the customer is not lost because it might fall down somewhere. The next step says check balance in the account laser. The next step says write a debit entry into the laser which means that money is being withdrawn and update the balance amount. The next step says count cash and hand it over to the customer. Frankly, the banking transaction has ended here, but look at the job card details. The last step says thank the customer for banking with your bank. This indeed is the complete procedure which every cashier of that bank will follow. The importance of this written procedure is that even if the regular cashier is absent and some other employee is asked to do the job of a cashier that employee can simply sit on the cashier's chair and carry out these steps exactly in this fashion. Please note that for a customer the experience will be identical independent of who is the person sitting on the cashier's chair. This is the importance of well written procedures, well documented procedures. In summary, a written procedure must first be fully read and understood and then all steps must be executed in the specified order. This is the importance of written procedures and this written procedure forms the basis of all our further discussion on computer programs.