Specimen Question Paper - Paper 1 Edexcel Computer Science IGCSE

Answer ALL questions. Write your answers in the spaces provided. Some questions must be answered with a cross in a box . If you change your mind about an answer, put a line through the box and then mark your new answer with a cross . 1 Characters, numbers and colours are examples of data that can be represented in a computing device. (a) Give one limitation of the ASCII character set. (1) ............................................................................................................................... ............................................................................................................................... ...................... ............................................................................................................................... ............................................................................................................................... ...................... ............................................................................................................................... ............................................................................................................................... ...................... ............................................................................................................................... ............................................................................................................................... ...................... (b) Complete the table to show the results of applying a Caesar cipher. (3) Plain text Shift Cipher text WINDOW +4 -3 AOFSB CACHE ECEJG (c) Here is a string of data. SSSSB W W Convert the string using a run-length encoding algorithm. (1) ............................................................................................................................... ............................................................................................................................... ...................... ............................................................................................................................... ............................................................................................................................... ...................... ............................................................................................................................... ............................................................................................................................... ...................... (d) Identify the 8-bit binary equivalent of the denary number 77. A B C D (e) One characteristic of lossy compression is that it makes files smaller. Give one other characteristic of lossy compression. (1) (1) ............................................................................................................................... ............................................................................................................................... ...................... ............................................................................................................................... ............................................................................................................................... ...................... (Total for Question 1 = 7 marks) 2 Networks are composed of hardware components arranged in topologies. They use protocols and addresses to make sure that data can be exchanged between nodes. (a) This is an example of an IPv4 address: 192.168.1.253 The expression for the maximum number of IPv4 addresses is 28 × 28 × 28 × 28 An example of an IPv6 address is 2001:2a4c:9d38:6abd:1820:43fc:3f57:febc Construct an expression for the maximum number of IPv6 addresses.