Computer Organization I Test 1/Version 1 CMSC 2833 Autumn 2007

Transcription

1 . Print your name on your scantron in the space labeled NAME. 2. Print CMSC 2833 in the space labeled SUBJECT. 3. Print the date, , in the space labeled DATE. 4. Print your CRN, 2393, in the space labeled PERIOD. 5. Print the test number and version, T/V, in the space labeled TEST NO. 6. This is a closed-book examination. No reference materials are permitted. No notes are permitted. 7. You may not consult your neighbors, colleagues, or fellow students to answer the questions on this test. 8. Cellular phones are prohibited. The possessor of a cellular phone will receive a zero (0) if the phone rings or is visible during the test. 9. You may use your personal calculator on this test. You are prohibited from loaning your calculator or borrowing a calculator from another person enrolled in this course. 0. Mark the best selection that satisfies the question. If selection b is better that selections a and d, then mark selection b. Mark only one selection.. Darken your selections completely. Make a heavy black mark that completely fills your selection. 2. Answer all 25 questions. 3. Record your answers on SCANTRON form 882-E (It is green!)

2 . ind the correct reduced expression for ( A, implemented in figure. a. = AD+ CD + ABC b. = AD + CD + ABC c. = AD + CD + ABC d. = AD + CD + ABC A B C D 2. The hexadecimal value CAD is equal to a octal b. 350 decimal c binary d base 4 igure. ( A, 3. ind the correct expression (not reduced) for ( A, implemented in figure 3 A B C D igure 3. ( A, a. = ABC + ACD + CD b. = ABC + ACD + CD c. = ABC + ACD + CD d. = ABC + ACD + CD 2

3 4. ind the optimal 2-level POS expression for X ( A, where ABCD is a 4-bit BCD code and WXYZ is an excess-6 code. Six is added to every valid BCD code in an excess-6 code. Inputs Outputs Decimal A B C D W X Y Z a. X ( A, = BC + BC b. X ( A, = ( B + ( B + c. X ( A, = B C + BC d. X ( A, = ( B + ( B + 5. ind the hexadecimal codes for the ASCII sequence 'Exam'. The decimal code for the letter A is 65 and the difference between the codes for the lower case letters and the upper case letters is 32. or example, the decimal code for the letter a is 97. a D b D c D d E 3

4 6. Which circuit diagram in figure 6.2 correctly implements function mapped in figure 6.? WX YZ igure 6. ( W, X, Y, Z ) W Z Y X Z W Z Y X Z W Z Y X Z W Z Y X Z a) b) igure 6.2 Implementations of mapped in figure 6.. c) d) 7. Convert MIND base 27 to base 3. a b c d ind the decimal equivalent of the eight's complement number a b c d

5 9. A trit is a three-state device. How many trits are needed to express the decimal number a. 7 b. 0 c. 9 d ind the optimal 2-level SOP expression for ( A, W where ABCD is a 4-bit BCD code and WXYZ is an excess-6 code. Six is added to every valid BCD code in an excess-6 code. Inputs Outputs Decimal A B C D W X Y Z a. W ( A, = BC + AB + A B C 0 b. W ( A, = BC + AB + AB c. W ( A, = BC + BC + AC d. W ( A, = A + B + C. What is the largest decimal integer that can be expressed in 3 bits? a. 25 b. 89 c d. 69 5

6 2. ind the minterm expression for W ( A, where ABCD is a 4-bit BCD code and WXYZ is an excess-6 code. Six is added to every valid BCD code in an excess-6 code. Inputs Outputs Decimal A B C D W X Y Z a. W A, m(2,3,4,5,6,7,8,9), d = b. W A, M (2,3,4,5,6,7,8,9), d = c. W A, M (2,3,4,5,6,7,8,9), d = d. W A, m(2,3,4,5,6,7,8,9), d = ( = m(0,,2, 3,4, 5) ( = M (0,, 2, 3, 4, 5) ( = M (0,,2,3,4,5) ( = m(0,, 2,3, 4,5) 3. ind the four's complement of a b. 02. c. 33. d Refer to figures 3. and 3.2 and the explanatory text. The wind velocity at 8 hours was 6 mph, at 9 hours it was 3 mph, and at 20 hours it was mph. What was the average of recorded values for the duration t, where 8 t 20? a mph b. 00 c. 0 d mph 6

7 Wind velocity (mph) Time (hours) Voltage (Volts) igure 3. Wind velocity Sampling point Time (hours) igure 3.2 Voltage Wind velocity is measured by a device that produces a 5-bit, 2 s complement voltage. Each single bit increment is equivalent to 0.2 Volts and -3 Volts is recorded as the 5-bit, 2 s complement value of Wind velocity is sampled every two hours, starting at zero hours, and recorded to the nearest whole number of miles per hour. The velocity recorded is valid for two hours beginning at the time sampled and extending to the next sample time. 7

8 5. How many bits are required to encode a single letter of a 270-letter alphabet? a. 9 b. 7 c. 0 d Refer to figures 3. and 3.2 and the explanatory text. What is the maximum value recorded by the device that measures wind velocity? a b. 20 mph c d. Volt 7. Refer to figures 3. and 3.2 and the explanatory text. What value was recorded at four hours? a. 000 b. 00 c. 00 d ind the hexadecimal sequence to send each of the characters of 'Exam' with odd parity. A parity bit is appended onto a 7-bit ASCII character. The parity bit is the rightmost bit of every 8-bit message. The decimal code for the letter A is 65 and the difference between the codes for the lower case letters and the upper case letters is 32. or example, the decimal code for the letter a is 97. a. 8AC2DC b. CBC2DA c. 8AC2DA d D 9. The hexadecimal value ACE is equal to a decimal b base 4 c octal d binary ( is the POS form of? 20. Which expression for A, = AC + AC a. ( A, = ( A + ( A + b. ( A, = AC + AC c. ( A, = ( A + ( A + d. ( A, = AC + AC 8

9 2. ind the maxterm expression for ( A, WXYZ is an excess-6 code. Six is added to every valid BCD code in an excess-6 code. X where ABCD is a 4-bit BCD code and Inputs Outputs Decimal A B C D W X Y Z a. X ( A, m(2,3,4,5), d = m b. X A, m(0,,6,7,8,9), d = c. X ( A, M (2,3,4,5), d = M d. X A, M (0,,6,7,8,9), d = = (0,, 2,3, 4,5) ( = m(0,, 2,3, 4,5) = (0,, 2, 3, 4, 5) ( = M (0,, 2,3, 4,5) 22. Which of the identities given in below figure 2 is not a basic identity of Boolean algebra? a. X + = b. X + X = X c. X + Y = X + Y d. X + X = 23. Which transition fails the test for a Gray code sequence? a > 000 b. 00 -> 000 c. 0 -> 00 d. 00 -> ind the two's complement representation of in an 8-bit field where the leftmost 4 bits represent the integer portion and the rightmost 4 bits represent the fractional portion. a. 000 b. 000 c d The decimal value is equal to a binary b base 4. c. CAE.48 hexadecimal d octal 9