计算机概论 1.(15%) Security A small private club has only 100 members. Answer the following question: a) How many secret keys are needed if all members of the club need to send secret messages to each other? b) How many secret keys are needed in the folloeing scenario? Everyone trusts the president of the club. If a member needs to send a message to another member, they first send it to the president, and the president then sends the message to the other member. c) How many secret keys are needed if the president decides that the two members who need to communicate should contact him first. The temporary key is encrypteand sent to both members. 2.(25%) Number system a) What is the binary representation of (7 + 5/8)? b) Using an 8-bit allocation, first convert each of the following integers to two's complement, do the operation, and then convert the result to decimal. (1) 12 + 49 (2) 13 - 60 c) What value is represented by the bit pattern 01111101 when interpreted using floating-point format in which the most significant bit is the sign bit, the next three bits represent the exponent field in excess notation, and the last four bits represent the mantissa? d) How many errors in a single code pattern could be corrected when using an error-correcting code in which each pattern is a Hamming distance of at least seven from any other code pattern? 3.(10%) Data Compression a) Encode the following characters using Huffman coding with the given frequencies: A(8), B(12), C(25), D(20), E(15), F(17), G(6) b) Encode the message "xxy zzy xxy" using the LZW method, and then decode the encoded message to get the original message. 4.(15%) The following table shows a portion of a machine's memory containing a program written in the language described in the language description table. Answer the questions below assuming that the machine is started with its program counter containing 00. address contnet address contnet 00 10 07 00 01 02 08 C0 02 24 09 00 03 04 0A C0 04 B4 0B 00 05 0A 0C C0 06 C0 0D 00 a) What bit pattern will be in register 0 when the machine halts? b) What bit pattern will be in register 4 when the machine halts? c) What bit pattern will be in the program counter when the machine halts? 5.(10%) Operating System A process that is waiting for a time slice is said to suffer starvation if it is never given a time slice. There are two lines for customers to line up in the bank, one is for normal people, and the other is for VIP. The bank will serve the VIP first and then serve the normal people. Think in this situation whether the starvation will happen? If it will happen, how will you suggest the bank to avoid this program by the rule that the VIP customer never wait a longer than the normal customer who arrived the bank at the same time? 6.(5%) List three types of processing you know. And tell what differences between each other briefly. 7.(25%) Networking and Internet a) What is a protocol? b) Write the full name and describe briefly the purpose of the following protocol. (1)HTTP, (2)SMTP c) Suppose the IP address of the computer is quoted as 192.168.55.66. What is the 32-bit address in hexdecimal notation? d) Identify the components of the following URL and describe the meaning of each http://c.csie.org/~wangshichen/Intro2010/index.html 8.(15%) Algorithm Suppose we apply Test1(defined belows) to the input list (A,b,C,E,G,H,I,J,L,N,O,P,Q,X,Y). Please write down the output of finding Z. procedure Test1(list, TargetValue) if(list empty) then Print 0 else select the "middle" entry in entry to be the TestEntry case 1: if TargetValue = TestEntry print the TargetValue case 2: if TargetValue < TestEntry apply procedure Test1 to see if TargetValue is in the preceding TestEntry case 3: if TargetValue > TestEntry apply procedure Test1 to see if TargetValue is in the following TestEntry Print the TestEntry end if ※ 编辑: danielu0601 来自: 140.112.30.136 (10/31 11:30)