Keep on learning   There are more than 800 courses on OpenLearn for you to 8.3 The AND operation The AND operation combines two binary words bit by bit according to the rules 0 AND 0 = 0 0 AND 1 = 0 1 AND 0 = 0 1 AND 1 = 1 In other words, only when both bits are 1 is the result 1. You may find it helpful to think of it this way: when one bit is one and the other bit is 1 the result is 1. 7.5 Dividing 2's complement integers Just as multiplication can be turned into repeated additions, so division can be turned into repeated subtractions. And just as shifting a binary integer one place to the left equates to multiplying by two, so shifting a binary integer one place to the right equates to dividing by two. 7.4 Multiplying 2's complement integers Multiplication can be thought of as repeated addition. For instance, in denary arithmetic 7 × 5 can be thought of as 7 + 7 + 7 + 7 + 7 There is therefore no need for a new process for the multiplication of binary integers; multiplication can be transformed into repeated addition. In multiplication the result is very often much larger than either of the two integers being multiplied, and so a multiple-length representation may be needed to hold the result of a mu 2.2.3 Positive integers: converting denary numbers to binary If computers encode the denary numbers of the everyday world as binary numbers, then clearly there needs to be conversion from denary to binary and vice versa. You have just seen how to convert binary numbers to denary, because I did a couple of examples to show you how binary numbers ‘work’. But how can denary numbers be converted to binary? I'll show you by means of an example. 2.2.2 Positive integers: binary numbers Just as a denary number system uses ten different digits (0, 1, 2, 3, … 9), a binary number system uses two (0, 1). Once again the idea of positional notation is important. You have just seen that the weightings which apply to the digits in a denary number are the exponents of ten. With binary numbers, where only two digits are used, the weightings applied to the digits are exponents of two. The rightmost bit is given the weighting of 2°, which is 1. The ne Acknowledgements Except for third party materials and otherwise stated (see terms and conditions). This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence 17.2 The checkout terminal The first computer block represents the checkout terminal. The processes at the checkout (receiving, storing, retrieving, manipulating and sending data to the user), are the same as I described earlier. However, the checkout terminal also sends data via the supermarket's network. 16.2.2 Storing and retrieving data As each item is scanned, the checkout computer looks up its price. The running total for each customer's purchases is stored temporarily in the checkout terminal. Other data may also be stored, such as the amount of money that has been taken at that checkout during the day. 4.2.3 Second computer (the FirstClass server) The computer on the right of Figure 11 receives the data, manipulates it and then stores it. The computer then typically sends some kind of response back via the network, which may require the computer to retrieve some stored data. The computer in this example is one of the Open University's FirstClass servers. A server 13.4 Flash memory
Flash memory is an electronic form of memory which can be used, erased and reused. A flash memory card is a small storage device used to store data such as text, pictures, sound and video. These cards are used in portable devices such as digital cameras and in small portable computers, such as Personal Digital Assistants (PDAs). A USB flash memory, sometimes called a 'memory stick', is a small storage device which is completely external and connects to the computer via a USB por 13.3 Optical storage
A CD-ROM (Compact Disk Read Only Memory) uses a laser-based optical form of storage. This type of disk has been used for many years to distribute music and computer software. A CD-ROM drive is needed to read the disks. Data is locked into the disk during manufacture, and cannot afterwards be changed. There are two other types of CD device for computers: CD-R (CD-recordable) and CD-RW (CD-rewritable). With the right sort of CD drive in your computer, you can 'burn' data (that is, 13.2 Magnetic storage As I mentioned earlier, your computer has a hard disk which provides a permanent storage area for your computer's programs and the files you create. When you save files to your computer's hard disk, you are using a magnetic storage medium. Data stored in magnetic form can be changed once it has been stored, so if you run out of space you can delete some files to make room or, if you want to edit a file, you can make the necessary changes and then save it again. At the time of writing, a mediu 4.1 Introduction I'll now look at what these components do in the communication system, using the mobile phone system as an example. 3.2 Looking into the 'means of conveying a message' The diagram in Figure 6 shows that, for communication to take place, there needs to be some means of conveying the message between the sender and the recipient. I am now going to look at the essential components of 'means of conveying a message'. In other words, I shall treat 'means of conveying a message' as a system and look at Introduction This course will help you understand how arguments are constructed and used in the Social Sciences. The material is primarily an audio file, originally 30 minutes in length and recorded in 1998. This OpenLearn course provides a sample of Level 1 study in Sociology. 1.6.2 Different types of sound Sounds come in four categories. Sound effects. Many UIs contain a range of warning beeps and reassuring sounds confirming that operations have been completed. These can include naturalistic sounds, such as the sound of a piece of screwed-up paper dropping into a waste paper basket. Music. Many composers use computer systems to compose music, and programs such as games make extensive use of music. Short sequences of musical 1.6.1 The role of sound The use of sound is becoming increasingly common, particularly for the following types of application. Applications where the eyes and attention are required away from the screen. Relevant examples include flight decks, medical applications, industrial machinery and transport. If you are a runner, you may have a heart rate monitor that allows you to monitor how fast your heart is beating. This is often indicated by an auditory beep, which speeds Acknowledgements Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence Figure 1 ENIAC Computer. Photo © Science Photo Library Rozin, D. ‘Wooden Mirror’, 7.3 Using flowcharts to describe a task Application programs are designed to perform specific tasks. These tasks range from the relatively simple to the extremely complex. In this section you will look at what is involved in planning a program to perform some simple tasks. In order to write a program, the task the program will perform has to be first written as a list of actions. The actions have to be given in an order that will ensure the task is carried out successfully.
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