ECS 89L: Computer Science For Biologists



ECS 15: Introduction to Computers

Midterm

Notes:

1) The midterm is open book, open notes.

2) No wandering eyes or unauthorized leaving of the exam room.

3) Please write your name at the top right of each page you turn in!

4) Please, check your work! If possible, show your work when multiple steps are involved.

1) How many bytes are there in one Megabyte (MB)? 2pts

a. 1,000,000

b. 1,000,024

c. 1,048,576

d. 1,024,000

2) Which of the following is NOT a valid HTML tag: 2pts

a.

b.

c.

d.

3) An operating system is: 2pts

a. a maintenance program should the computer crash

b. the firmware stored on ROM to boot the system

c. the software that manages the sharing of the resources of a computer

d. another name for the manual that explains how to use the computer

4) Which binary number comes right after the binary number 101111 2pts

a. 101112

b. 110000

c. 111000

d. 111111

5) Assume you are preparing a term paper and want to use the Web as a source of information. Which of the following statements is TRUE? 2pts

a. You are free to copy information you find on the Web and include it in your paper

b. You do not have to cite the Web sources you use for your paper

c. You should never consult the Web when you are working on a paper

d. Just like print sources, Web sources must be cited in your paper. You are not free to plagiarize information you find on the Web.

6) If we go from 8 bits to 9 bits of quantization the number of distinct levels that can be recorded: 2pts

a. Stays the same

b. Increases by one

c. Doubles

d. Quadruples

7) If we go from 8 bits to 10 bits of quantization the number of distinct levels that can be recorded: 2pts

a. Increases by two

b. Doubles

c. Triples

d. Quadruples

8) To run several programs apparently simultaneously on a computer, you need: 2pts

a. As many CPU or computing cores as programs that you want to run simultaneously

b. An operating system that allows multi-threading

c. An operating system that allows multi-tasking

d. A super-computer; no personal computers or laptops can run several programs apparently simultaneously.

9) If a computer fails the POST, it is likely that: 2pts

a. The operating system has crashed,

b. One application is using more memory than it has asked for,

c. The Master Boot Record is empty,

d. One piece of hardware attached to the computer has failed.

10) Which of the following retains its information when the computer is turned off?

a. ROM 2pts

b. CPU

c. RAM

d. GPU

11) 1024 bits correspond to N bytes, where N is: 3pts

a. 8192

b. 128

c. 1024

d. 10

12) A computer’s BIOS does not: 3pts

a. Shutdown the computer

b. Identify component hardware

c. Prepare the computer so that other programs can load and execute

d. Be loaded first when the computer is turned on

13) The base 10 equivalent of the hexadecimal 1AD is 5pts

Recall A=10 and D=13 in hexadecimal

1AD = (1*162) + (10*16) + (14*1) = (1*256) + (10*16) + (13) = 256 + 160 + 13

= 429

14) What is the maximum number that can be stored in a half of a byte? 5pts

A byte is 8 bits. Half a byte is 4 bits. The biggest number that can be stored in a bit:

1111 = 23 + 22 + 2 + 1 = 8 + 4 + 2 + 1 = 15

(Note this is also equal to 24-1)

15) What is the maximum number that can be stored in N bits? 5pts

Max number in N bits is equal to 2N-1.

16) Assume the human heart beats at 60 beats per second. To get the right measurement of the heart dynamics, at what rate do you sample? (Express the answer in Hz.) 5pts

Via Nyquist theorem, sample at twice the highest frequency, so 120 Hz.

17) If each data point is stored in 16 bits, how many BYTES of data would you need to store 10 minutes of human heart beat data? 5pts

(120 samples/sec)*(16 bits/sample)*(1 byte/8 bits)*(60 sec/min)*(10min) = 144,000 bytes

Part III. For the next portion, examine the statement, indication if it is or is not a proposition. If it is a proposition, indicate its truth value (otherwise indicate N/A). 2pts each line

|Statement |Proposition |T or F or N/A |

| |(Y or N) | |

|The cute cat |N |N/A |

|X = Y + 2 |N |N/A |

|Study hard |N |N/A |

|Is the cat cute? |N |N/A |

|The moon is made of green cheese |Y |F |

|This statement is false |N |N/A |

|This is a statement |Y |T |

Part IV Logical implications

Consider the following propositions:

P = You learn the basics of computers

Q = You get a good job

Assume the implication P -> Q is True. Assess whether the following statement is logically correct or logically flawed.

1) You did not learn the basics of computers so you do not have a good job. 2pts

a. Logically correct

b. Logically flawed (Claims not(P) -> not(Q), but there can exist good jobs that don’t use computers.)

2) You have a good job, so you learned the basics of computers. 2pts

a. Logically correct

b. Logically flawed (Claims Q -> P, but again there can exist good jobs that don’t use computers.)

3) You do not have a good job so you did not learn the basics of computers. 2pts

a. Logically correct (Claims not(Q) -> not(P).)

b. Logically flawed

Part V

Look carefully at the logical circuit below, and complete the table. Remember: an input of 0 means switch off/open/no current flows, while an input of one means switch on and current flows.

[pic]

1pt each 2pts each

|Input A |Input B |Intermediate output |Output |

|1 |1 |0 |1 |

|1 |0 |0 |1 |

|0 |1 |1 |0 |

|0 |0 |1 |1 |

This may not be a simple AND or OR gate, but can you write an expression using AND, OR, and NOT for the operation on inputs A and B that the gate implements?

NOT (Not(A) AND B) = (NOT(A) NAND B) = A OR NOT(B) 2pts

________________________________________

Part VI. The table below lists on the left devices that can be found inside a computer. For each of these devices, give their purpose (center column), and list in the right column what could happen if they would stop working

5 pts in total each row.

|Component |What it does |Possible problem |

|Motherboard |Backbone of the computer, houses many hardware devices |Many problems, from the computer not booting, |

| |(CPU, RAM, Hard drive, buses) and many interfaces for |to certain devices (hard drive, keyboard, etc) |

| |additional hardware (keyboards, mice, internet interface, |not working properly. |

| |power supply connector) | |

|BIOS EPROM chip |The Erasable Programmable Memory Chip that stores the |The BIOS won’t run and the computer will not |

| |firmware to initiate and run the Basic Input/Output system|boot. |

| |installed by the computer manufacturer. | |

|Bus between the CPU and RAM |Transports electronic signals, and hence data, between the|No data, or erroneous data, will be loaded into|

| |Central Processing Unit and the Random Access Memory. |the CPU. |

| | | |

| | | |

| | | |

| | | |

| | | |

| | | |

| | | |

Extra credit: Fill out the table below.

[pic]

|Input A |Input B |Input C |Output |

|1 |1 |1 |0 |

|1 |1 |0 |1 |

|1 |0 |1 |0 |

|1 |0 |0 |1 |

|0 |1 |1 |0 |

|0 |1 |0 |1 |

|0 |0 |1 |1 |

|0 |0 |0 |1 |

Extra credit: Convert 233 from base 10 to base 2

Number Number % 2 Remainder

233 116 1

116 58 0

58 29 0

29 14 1

14 7 0

7 3 1

3 1 1

1 0 1

Answer: 11101001

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