Computer Science - XI - Part I PDF

Class - XI Part - I Government of Kerala DEPARTMENT OF EDUCATION State Council of Educational Research and Training (SCERT); Kerala 2016 Dear students, Computer Science, a subject belonging to the d...

Class - XI Part - I Government of Kerala DEPARTMENT OF EDUCATION State Council of Educational Research and Training (SCERT); Kerala 2016 Dear students, Computer Science, a subject belonging to the discipline of Science and of utmost contemporary relevance, needs continuous updating. The Higher Secondary Computer Science syllabus has been revised with a view to bringing out its real spirit and dimension. The constant and remarkable developments in the field of computing as well as the endless opportunities of research in the field of Computer Science and Technology have been included. This textbook is prepared strictly in accordance with the revised syllabus for the academic year 2014 - 15. It begins with the historical developments in computing and familiarises the learner with the latest technological advancements in the field of computer hardware, software and network. The advancement in computer network, Internet technology, wireless and mobile communication are also dealt with extensively in the content. In addition to familiarising various services over the Internet, the need to be concerned about the factors that harness morality and the awareness to refrain from cyber security threats are also highlighted. The major part of the textbook as well as the syllabus establishes a strong foundation to construct and enhance the problem solving and programming skills of the learner. The multi-paradigm programming language C++ is presented to develop programs which enable computers to manage different real life applications effectively. The concepts and constructs of the principles of programming are introduced in such a way that the learner can grasp the logic and implementation methods easily. I hope this book will meet all the requirements for stepping to levels of higher education in Computer Science and pave your way to the peak of success. Wish you all success. Dr P. A. Fathima Director, SCERT; Kerala  3. As a result of carrying out the instructions, some outputs (here, omlette) are obtained. The instructions given to process the inputs are, however, not precise. They are ambiguous. For example, the interpretation of "till the side is fried" in step 5 and "fried well" in step 6 can vary from person to person. Due to such imprecise instructions, different persons following the same recipe with the same inputs can produce omlettes which differ in size, shape and taste. The above ambiguities should be avoided while writing steps to solve the problems using the computer. a. Algorithm Mathematicians trace the origin of the word algorithm to a famous Arab mathematician, Abu Jafar Mohammed Ibn Musaa Al-Khowarizmi. The word 'algorithm' is derived from the last part of his name Al-Khowarizmi. In computer terminology an algorithm may be defined as a finite sequence of instructions to solve a problem. It is a step-by-step procedure to solve a problem, where each step represents a specific task to be carried out. However, in order to qualify an algorithm, a sequence Fig. 4.4 : Abu Jafar Mohammed of instructions must possess the following Ibn Musaa Al-Khowarizmi (780 - 850) characteristics: (i) It should begin with instruction(s) to accept inputs. These inputs are processed by subsequent instructions. Sometimes, the data to be processed will be given along with the problem. In such situations, there will be no input instruction at the beginning of the algorithm. (ii) Use variables to refer the data, where variables are user-defined words consisting of alphabets and numerals that are similar to those used in mathematics. Variables must be used for inputting data and assigning values or results. (iii) Each and every instruction should be precise and unambiguous. In other words, the instructions must not be vague. It must be possible to carry them out. For example, the instruction "Catch the day" is precise, but cannot be carried out. (iv) Each instruction must be sufficiently basic such that it can, in principle, be carried out in finite time by a person with paper and pencil. (v) The total time to carry out all the steps in the algorithm must be finite. As algorithm may contain instructions to repetitively carry out a group of instructions, this requirement implies that the number of repetitions must be finite. (vi) After performing the instructions given in the algorithm, the desired results (outputs) must be obtained. 114  6. Data Types and Operators The exact sizes of these data types depend on the compiler and computer you are using. It is guaranteed that: a double is at least as big as a float. a long double is at least as big as a double. Each type and their modifiers are listed in Table 6.1 (based on GCC compiler) with their features. Name Description Size Range char Character 1 byte signed: -128 to 127 unsigned: 0 to 255 short int Short Integer 2 bytes signed: -32768 to 32767 (short) unsigned: 0 to 65535 int Integer 4 bytes signed: -2147483648 to 2147483647 unsigned: 0 to 4294967295 long int Long integer 4 bytes signed: -2147483648 to 2147483647 (long) unsigned: 0 to 4294967295 +/-38 Floating point number 4 bytes -3.4×10 to +3.4 × 10+/-38 with float approximately 7 significant digits double Double precision 8 bytes -1.7 × 10+/-308 to +1.7 × 10+/-308 with floating point number approximately 15 significant digits long Long double precision 12 bytes -3.4 × 10+/-4932 to +3.4 ×10+/-4932 With double floating point number approximately 19 significant digits Table 6.1: Data type and type modifiers The values listed in Table 6.1 are only sample values to give you a general idea of how the types differ. The values for any of these entries may be different on your system. 6.5 Variables Memory locations are to be identified to refer data. Variables are the names given to memory locations. These are identifiers of C++ by which memory locations are referenced to store or retrieve data. The size and nature of data stored in a variable depends on the data type used to declare it. There are three important aspects for a variable. 149