ECS 89L: Computer Science For Biologists



ECS 15: Introduction to Computers

Midterm

You can complete this exam and turn it in as a .doc or .docx file via smartsite for extra credit. The deadline is 9:30am on Mon, Feb 11. I highly recommend you work on your own: your midterm will obviously have to be solo work. You may ask questions on smartsite chatroom about how to approach problems.

Indicate your answer to a multiple-choice question by changing the text to red for that option in this Word document. For instance:

0) Which of the following is not a requirement for ECS15:

a. Understand the basics of how computers work

b. Learn critical thinking and critical scientific writing

c. Build a programming language from scratch

d. Learn how to write a computer program

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.

Part I (these questions are multiple choices; in each case, find the most plausible answer)

 

1) How much memory is one gigabyte?

a. 1000 bytes

b. 1,073,741,824 bytes

c. 2100 bytes

d. 1,000,000,000 bytes

2) When your computer slows down significantly, it is likely that you may be

a. Running out of ROM

b. Running out of RAM

c. Running out of disk space

d. Have too much ROM

3) What is the first step of a CPU cycle?

a. Fetch the instruction

b. Clear the memory

c. Execute the instruction

d. Mix water and detergent

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

a.

b.

c.

d.

5) The memory bus connecting the CPU to the RAM

a. allows for extra storage of data

b. transports electrical signals and data between them

c. makes frequent stops, hence the name bus

d. oversees the fetch/execute cycles

6) A compiled program

a. is source code

b. can be run on all operating systems as is

c. typically runs more quickly than an interpreted program

d. is a collection of smaller programs, like a compilation

7) What steps are necessary for transforming a sound wave into digital data

a. sampling

b. sampling and quantization

c. sound waves are already digital

d. quantum measurement

8) Which of the following is NOT an operation performed by the BIOS:

a. Runs self-tests

b. Initiates the boot up process

c. Loads the operating system

d. Logs the name of the current user in a Biographies file, hence the name BIOS

9) How much space would you need to store a 10 min song that has been sampled at

44.1 KHz, with each data point stored on 16 bits, in stereo (assume no compression)?

a. About 100 Mbytes

(44,100sample/sec)(16 bits/sample)(2 channels)(10min)(60sec/min) = 846,720,000 bits. Then, (846,720,000 bits)(1byte/8bits) = 105,840,000 bytes.

b. About 100 Mbits

c. About 50 Mbytes

d. About 5 Mbytes

10)  The program that permits the computer to control and manage its own resources is called a(n)

a. GUI

b. operating system.           

c. CPU         

d. BIOS.

11) Which of the following is not a property that an operating system may have:

a. Multitasking

b. Multiprocessing

c. Multimodal

d. Multithreading

Part II Short answer

12) The binary equivalent of the hexadecimal 5F is

5F = (5*16) + (15*1) = 95

95 = 1011111 in binary

13) Assume the wings of a bumblebee beat at 100 beats per second. What is the rate of beating expressed in Hz?

100 Hz

14) To get a correct measurement of a bumble bee wing dynamics, at what rate do you sample? (Express the answer in Hz.)

200 Hz (Nyquist theorem says to sample at twice the rate of highest frequency.)

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).

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

| |(Y or N) | |

|The dog is brown |Y |T, F, or N/A |

|1+5=10 |Y |F |

|X=10 |N |N/A |

|The brown dog |N |N/A |

|Is the dog brown? |N |N/A |

|Come inside right now! |N |N/A |

|I am lying |N |N/A |

|I am telling the truth |Y |T, F, or N/A |

Part IV Logical implications

Consider the following propositions:

P = It is sunny

Q = You go to the beach

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

1) You are at the beach, so it is sunny.

a. Logically correct

b. Logically flawed (it says Q ( P, but there are several things that could cause Q)

2) It is not sunny so you did not go to the beach.

a. Logically correct

b. Logically flawed (it says not(P) ( not(Q), but several things could cause Q))

3) You did not go to the beach, so it is not sunny.

a. Logically correct (it says not(Q) ( not(P); remember Q is necessary for 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]

|Input A |Input B |Output of A (4pts) |Output (8pts) |

|1 |1 |0 |0 |

|1 |0 |0 |1 |

|0 |1 |1 |0 |

|0 |0 |1 |0 |

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? (4pts)

A AND NOT(B), also NOT(A) NOR (B) = NOT(NOT(A) OR B)

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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 each row; 3pts what is does/ 2pts problem)

|Component |What it does |Possible problem |

|RAM |Random Access Memory for temporary storage of data. |Thrashing computer and no data fetched or |

| | |stored in memory |

| | | |

| | | |

| | | |

| | | |

| | | |

|ROM |Read-only-memory usually programmed by the computer |Computer will not boot up. |

| |manufacturer, holding crucial data used in the boot up | |

| |process. | |

| | | |

| | | |

| | | |

| | | |

| | | |

|Arithmetic Logic Unit |The part of the CPU that executes logic and arithmetic |No data processing (CPU will not perform any |

| |operations. It also fetches and stores data in memory |logic or arithmetic operations. |

| |locations. | |

| | | |

| | | |

| | | |

| | | |

| | | |

| | | |

| | | |

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