UMUC ITEC 625 ITEC/625 ITEC625 Midterm Solutions


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ITEC 625 Computer Systems Architecture Midterm Exam Answers

I. For each statement below, Explain Why it is True or False (2 points each1 point for correct answer of True or False, another 1 point for explanation)

 1) Secondary storage is often equated with main memory in von Neumann architecture.

2) Program execution consists of repeating the process of instruction fetch and instruction execution.

3) Addition and subtraction can be performed on numbers in two’s complement notation by treating them as unsigned integers.

4) One drawback of sign-and-magnitude representation is that there are two representations of 0.

5) Both sign-and-magnitude representation and twos complement representation use the most significant bit as a sign bit

6) When you want to represent -0.0000000000001 as an 8-bit float point number but the float point system cannot represent it due to limit of bits, you have a negative overflow.

7) The value of an unsigned integer is interpreted as the magnitude of its underlying binary pattern.

8) RISC systems typically have a small ISA (fewer instructions) but make up for it with faster hardware.

9) ALU reads the instructions, and generates the necessary digital signals to operate the other components.

10) Superscalar architectures allow several instructions to be issued and completed per clock cycle.

II. Multiple Choices – Choose ONLY 1 Answer (2 points each, 20 points total)


1. Which of the following sentences about 8-bit two’s complement is correct?


2. The processing required for a single instruction is called a(n) __________ cycle.


3. In ________ representation the rule for forming the negation of an integer is to invert the sign bit.


4. ________ is when the result may be larger than can be held in the word size being used.


5. Positive numbers less than 2-183 (i.e. 10-55 in the book) could cause ________.


6. During the _________ the Little Man goes to the mailbox address specified in the instruction he previously fetched.


7. The __________ interprets the instructions in memory and causes them to be executed.


8. Which of the following sentences about IEEE 754 single precision floating point numbers is correct?


9. The von Neumann architecture has which of the following features?


10. The binary string 1011 1000 1111 is equivalent to __________.


III. Short Answers (2 points each12 points total) 


1. Virtualization is a concept that is used in many areas such as virtual memory and virtual machine. Use your experience to explain what is meant by virtualization, and what are the benefits and weakness of virtualization.


2. Analyze the benefits and challenges of quantum computing, and explain why most of the current quantum computers are in theoretical stages instead of large-scale production.


3. The input data values in our Little Man Computer have always been entered in the order that they were to be used. Can you find ways to accept input in (1) reverse order and (2) wrong order, and still use the input correctly?


4. Give an example that shows the disadvantage of using a sign-and-magnitude format for manipulating signed integers.


5. Most modern computers use superscalar and VLIW. Explain the performance benefits obtained from superscalar and VLIW.


6. What are the trade-offs in using a serial bus vs a parallel bus to move data from one place to another?


IV. 2’s Complement (3 points each12 points total)  


The following are 2’s complement numbers, note they are binary numbers of four bits. Calculate the number expressions, and tell whether there is an overflow. Use binary and decimal calculation to prove your answer.


V. For an m-bit binary integer number, what is the largest positive number and what is the smallest negative number (i.e. negative number with largest absolute value) that it can represent? Please prove your answer. (4 points)  


VIFor the following IEEE 754 format numbers, write out the equivalent decimal numbers (Please show your calculation steps). (4 points each, total 8 points)  


VIIEach row in the following table contains the same number in different number formats, namely binary, octal, decimal, and hexadecimal. Please fill out the missing numbers, and use 12-bit 2’s complement for negative binary values. (1 point for each answer in a blank space)  


Using the Little Man Computer and Instruction Set, answer the following questions:


1. Write a LMC program, which takes 2 input values, say A and B, and then outputs all integers between these two values. (Note: There are two possible cases: A ≤ B, or A > B, you need to write the program that is capable of handling both cases. For the integers between A and B, however, your program can output in either ascending or descending order. )


2. Create a LMC program to output the first N Fibonacci numbers. Your program should take the input N and then output the first N elements of the sequence. i.e. 1, 1, 2, 3, 5… (Definition of Fibonacci numbers can be found at