feedback.json

{
    "gradio_feedback": [
        {
            "question": "What is a Finite State Machine?",
            "generated_answer_1": "Afinite state machine (orFSM) is a model for understanding the behavior of a system by describin g the system as occupying one of a finite set of states, moving betwe en these states in response to external inputs, and producing external outputs.",
            "context_1": "page_content='82  3.1.3 Finite State Machines A\ufb01nite state machine (orFSM) is a model for understanding the behavior of a system by describin g the system as occupying one of a \ufb01nite set of states, moving betwe en these states in response to external inputs, and producing external outputs. In any given state, a pa rticular input may cause the FSM to move to another state; this combination is called a transition rule . An FSM comprises \ufb01ve parts: a \ufb01nite set of states, a set of possible inputs, a set of possible outputs, a set of transition rules, and methods for calculating outputs. When an FSM is implemented as a digital system, all states must be rep resented as patterns using a \ufb01xed number of bits, all inputs must be translated into bits, and all outpu ts must be translated into bits. For a digital FSM, transition rules must be complete ; in other words, given any state of the FSM, and any pattern of input bits, a transition must be de\ufb01ned from that state to another state (transitions from a state to itself, called self-loops , are acceptable). And, of course, calculation of outputs for a dig ital FSM reduces to Boolean logic expressions. In this class, we focus on clocked sync hronous FSM implementations, in which the FSM\u2019s internal state bits are stored in \ufb02ip-\ufb02ops. In this section, we introduce the tools used to describe, develop, a nd analyze implementations of FSMs with digital logic. In the next few weeks, we will show you how an FSM can se rve as the central control logic in a computer. At the same time, we will illustrate connections between F SMs and software and will make some connections with other areas of interest in ECE, such as the design and analysis of digital control systems. The table below gives a list of abstract states for a typical keyless entry system for a car. In this case, we have merely named the states rather than specifying the bit pat terns to be used for each state\u2014for this reason, we refer to them as abstract states. The description of the states in the \ufb01rst column is an optional element often included in the early design stages for an FSM, when ide ntifying the states needed for the design. A list may also include the outputs for each state. Again, in th e list below, we have speci\ufb01ed these outputs abstractly. By including outputs for each state, we implicit ly assume that outputs depend only on the state of the FSM. We discuss this assumption in more detail later in these notes (see \u201cMachine Models\u201d), but will make the assumption throughout our class. meaning state driver\u2019s door other doors alarm on vehicle locked LOCKED locked locked no driver door unlocked DRIVER unlocked locked no all doors unlocked UNLOCKED unlocked unlocked no alarm sounding ALARM locked locked yes Another tool used with FSMs is the next-state table (sometimes called a state transition table , or just astate table ), which maps the current state and input combination into the next state of the FSM. The abstract variant shown below outlines desired behavior at a high leve l, and is often ambiguous, incomplete, and even inconsistent. For example, what happens if a user pushes two buttons? What happens if they push unlock while the alarm is sounding? These questions should event ually be considered. However, we can already start to see the intended use of the design: starting f rom a locked car, a user can push \u201cunlock\u201d once to gain entry to the driver\u2019s seat, or push \u201cunlock\u201d twice to op en the car fully for passengers. To lock the car, a user can push the \u201clock\u201d button at any time. And, if a use r needs help, pressing the \u201cpanic\u201d button sets o\ufb00 an alarm. state action/input next state LOCKED push \u201cunlock\u201d DRIVER DRIVER push \u201cunlock\u201d UNLOCKED (any) push \u201clock\u201d LOCKED (any) push \u201cpanic\u201d ALARM' lookup_str='' metadata={'page_number': 87.0, 'textbook_name': 'ECE-120-student-notes'} lookup_index=0. Source: page 87 in ECE-120-student-notes",
            "feedback_1": "Like",
            "custom_answer_1": "",
            "generated_answer_2": "FSMs, we briefly discuss a powerful abstraction for formalizin g and reasoning about digital systems.",
            "context_2": "page_content='3.1 Serialization and Finite State Machines 79 ECE120: Introduction to Computer Engineering Notes Set 3.1 Serialization and Finite State Machines The third part of our class builds upon the basic combinational and se quential logic elements that we developed in the second part. After discussing a simple application of stored state to trade between area and performance, we introduce a powerful abstraction for formalizin g and reasoning about digital systems, the Finite State Machine (FSM). General FSM models are broadly applicab le in a range of engineering contexts, including not only hardware and software design but also the design o f control systems and distributed systems. We limit our model so as to avoid circuit timing issues in your \ufb01r st exposure, but provide some amount of discussion as to how, when, and why you should eventually learn the more sophisticated models. Through development a range of FSM examples, we illustrate importa nt design issues for these systems and motivateacoupleofmoreadvancedcombinationallogicdevicesthat canbe usedasbuilding blocks. Together with the idea of memory, another form of stored state, these elem ents form the basis for development of our \ufb01rst computer. At this point we return to the textbook, in whic h Chapters 4 and 5 provide a solid introduction to the von Neumann model of computing systems and t he LC-3 (Little Computer, version 3) instruction set architecture. By the end of this part of the cours e, you will have seen an example of the boundary between hardware and software, and will be ready to wr ite some instructions yourself. In this set of notes, we cover the \ufb01rst few parts of this material. W e begin by describing the conversion of bit-sliced designs into serial designs, which store a single bit slice\u2019s out put in \ufb02ip-\ufb02ops and then feed the outputs back into the bit slice in the next cycle. As a speci\ufb01c example, we use our bit-sliced comparator to discuss tradeo\ufb00s in area and performance. We introduce Finite S tate Machines and some of the tools used to design them, then develop a handful of simple counter desig ns. Before delving too deeply into FSM design issues, we spend a little time discussing other strategies for c ounter design and placing the material covered in our course in the broader context of digital system des ign. Remember that sections marked with an asterisk are provided solely for your interest, but you may need to learn this material in later classes. 3.1.1 Serialization: General Strategy In previous notes, we discussed and illustrated the development of bit-sliced logic, in which one designs a logic block to handle one bit of a multi-bit operation, then replicates th e bit slice logic to construct a design for the entire operation. We developed ripple carry adders in this wa y in Notes Set 2.3 and both unsigned and 2\u2019s complement comparators in Notes Set 2.4. Another interesting design strategy is serialization : rather than replicating the bit slice, we can use \ufb02ip- \ufb02ops to store the bits passed from one bit slice to the next, then pr esent the stored bits to the same bit slice in the next cycle. Thus, in a serial design, we only need one copy of th e bit slice logic! The area needed for a serial design is usually much less than for a bit-sliced design, but such a design is also usually slower. After illustrating the general design strategy, we\u2019ll consider thes e tradeo\ufb00s more carefully in the context of a detailed example. Recall the general bit-sliced design ap- proach, as illustrated to the right. Some number of copies of the logic for a single bit slice are connected in sequence. Each bit slice accepts Pbits of operand input and produces Qbits of external output. Adjacent bit slices receive an addi- tionalMbits of information from the previous bit slice and pass along Mbits to the next bit slice, generallyusing some representation chosen by the designer.P Qsecond bit sliceMP Qlast bit sliceMP QM Moutput logicRinitial values . . .first bit sliceresults per\u2212slice outputsper\u2212slice inputsa general bit\u2212sliced design The \ufb01rst bit slice is initialized by passing in constant values, and some ca lculation may be performed on the \ufb01nal bit slice\u2019s results to produce Rbits more external output.' lookup_str='' metadata={'page_number': 84.0, 'textbook_name': 'ECE-120-student-notes'} lookup_index=0. Source: page 84 in ECE-120-student-notes",
            "feedback_2": "Dislike",
            "custom_answer_2": "",
            "generated_answer_3": "a controllable twobit counter (with poorly chosen state values) Z1 Z0CLOCK H(halt button)",
            "context_3": "page_content='3.2 Finite State Machine Design Examples, Part I 99 3.2.11 Impact of the State Representation What happens if we choose a bad representation? For the same FSM \u2014the two-bit Gray code counter with start and stop inputs\u2014the table below shows a poorly chosen mappin g from states to internal state repre- sentation. Below the table is a diagram of an implementation using that representation. Verifying that the implementation\u2019s behavior is correct is left as an exercise for the det ermined reader. state S2S1S0 state S2S1S0 COUNT A 000 HALT A 111 COUNT B 101 HALT B 110 COUNT C 011 HALT C 100 COUNT D 010 HALT D 001 D QQ S0D QQ S1D QQ S2 G (go button)a controllable two\u2212bit counter (with poorly chosen state values) Z1 Z0CLOCK H(halt button)' lookup_str='' metadata={'page_number': 104.0, 'textbook_name': 'ECE-120-student-notes'} lookup_index=0. Source: page 104 in ECE-120-student-notes",
            "feedback_3": "Like",
            "custom_answer_3": ""
        },
        {
            "question": "what is a capacitor?",
            "generated_answer_1": "These memories have a finite number of storage elements, called bits, that can be accessed in any order.",
            "context_1": "page_content='3.6 Random Access Memories 117 ECE120: Introduction to Computer Engineering Notes Set 3.6 Random Access Memories This set of notes describes random access memories (RAMs), prov iding slightly more detail than is available in the textbook. We begin with a discussion of the memory abstractio n and the types of memory most commonly used in digital systems, then examine how one can build memo ries (static RAMs) using logic. We next introduce tri-state bu\ufb00ers as a way of simplifying ouput con nections, and illustrate how memory chips can be combined to provide larger and wider memories. A more de tailed description of dynamic RAMs \ufb01nishes this set. Sections marked with an asterisk are provided solely for you r interest, but you probably need to learn this material in later classes. 3.6.1 Memory A computer memory is a group of storage elements and the logic necessary to move data in and out of the elements. The size of the elements in a memory\u2014called the addressability of the memory\u2014varies from a single binary digit, or bit, to abyte(8 bits) or more. Typically, we refer to data elements larger than a byte aswords, but the size of a word depends on context. Each element in a memory is assigned a unique name, called an address, that allows an external circuit to identify the particular element of interest. These addresses ar e not unlike the street addresses that you use when you send a letter. Unlike street addresses, however, me mory addresses usually have little or no redundancy; eachpossiblecombinationofbitsinanaddressidenti\ufb01e sadistinctsetofbitsinthememory. The \ufb01gure on the right below illustrates the concept. Each house repre sents a storage element and is associated with a unique address. ADDR CSWEDATA\u2212IN DATA\u2212OUT100 101 110 111011 010 001 000k NN memory2   x Nk The memories that we consider in this class have severalproperties in common. These memories support two operations: writeplaces a word of data into an element, and readretrieves a copy of a word of data from an element. The memories are also volatile, which means that the data held by a memory are erased when electrical power is turned o\ufb00 or fails. Non-volatile forms of memory include magnetic and optical storage media such as DVDs, CD-ROMs, disks, and tapes, capacitive storag e media such as Flash drives, and some programmable logic devices. Finally, the memories considered in this cla ss arerandom access memories (RAMs) , which means that the time required to access an element in the memo ry is independent of the element being accessed. In contrast, serial memories such as magnetic tape require much less time to access data near the current location in the tape than data far aw ay from the current location. The \ufb01gure on the left above shows a generic RAM structure. The me mory contains 2kelements of Nbits each. Ak-bit address input, ADDR, identi\ufb01es the memory element of interest for any particular opera tion. The write enable input, WE, selects the operation to be performed: if WEis high, the operation is a write; if it is low, the operation is a read. Data to be written into an element ar e provided through Ninputs at the top, and data read from an element appear on Noutputs at the bottom. Finally, a chip select input, CS, functions as an enable control for the memory; when CSis low, the memory neither reads nor writes any location. Random access memory further divides into two important types: static RAM , orSRAM, anddynamic RAM, orDRAM. SRAM employs active logic in the form of a two-inverter loop to mainta in stored values.' lookup_str='' metadata={'page_number': 122.0, 'textbook_name': 'ECE-120-student-notes'} lookup_index=0. Source: page 122 in ECE-120-student-notes",
            "feedback_1": "Dislike",
            "custom_answer_1": "",
            "generated_answer_2": "smartphones and tablets.",
            "context_2": "page_content='2 chapter 1 WelcomeAboard Once we are comfortable with information represented as codes made up of 0s and 1s and operations (addition, for example) being performed on these repre- sentations, we will begin the process of showing how a computer works. Starting in Chapter 3, we will note that the computer is a piece of electronic equipment and, as such, consists of electronic parts operated by voltages and interconnected by wires. Every wire in the computer, at every moment in time, is at either a high voltage or a low voltage. For our representation of 0s and 1s, we do not specify exactly how high. We only care whether there is or is not a large enough voltage relative to 0 volts to identify it as a 1. That is, the absence or presence of a rea- sonable voltage relative to 0 volts is what determines whether it represents the value 0 or the value 1. In Chapter 3, we will see how the transistors that make up today\u2019s micro- processor (the heart of the modern computer) work. We will further see how those transistors are combined into larger structures that perform operations, such as addition, and into structures that allow us to save information for later use. In Chapter 4, we will combine these larger structures into the von Neumann machine, a basic model that describes how a computer works. We will also begin to study a simple computer, the LC-3. We will continue our study of the LC-3 in Chapter 5. LC-3 stands for Little Computer 3. We actually started with LC-1 but needed two more shots at it before (we think) we got it right! The LC-3 has all the important characteristics of the microprocessors that you may have already heard of, for example, the Intel 8088, which was used in the \ufb01rst IBM PCs back in 1981. Or the Motorola 68000, which was used in the Macintosh, vintage 1984. Or the Pentium IV, one of the high-performance microprocessors of choice for the PC in the year 2003. Or today\u2019s laptop and desktop microprocessors, the Intel Core processors \u2013 I3, I5, and I7. Or even the ARM microprocessors that are used in most smartphones today. That is, the LC-3 has all the important characteristics of these \u201creal\u201d microprocessors without being so complicated that it gets in the way of your understanding. Once we understand how the LC-3 works, the next step is to program it, \ufb01rst in its own language (Chapter 5 and Chapter 6), and then in a language called assembly language that is a little bit easier for humans to work with (Chap- ter 7). Chapter 8 introduces representations of information more complex than a simple number \u2013 stacks, queues, and character strings, and shows how to imple- ment them. Chapter 9 deals with the problem of getting information into (input) and out of (output) the LC-3. Chapter 9 also deals with services provided to a computer user by the operating system. We conclude the \ufb01rst half of the book (Chapter 10) with an extensive example, the simulation of a calculator, an app on most smartphones today. In the second half of the book (Chapters 11\u201320), we turn our attention to high-level programming concepts, which we introduce via the C and C++ programming languages. High-level languages enable programmers to more e\ufb00ectively develop complex software by abstracting away the details of the under- lying hardware. C and C++ in particular o\ufb00er a rich set of programmer-friendly constructs, but they are close enough to the hardware that we can examine how code is transformed to execute on the layers below. Our goal is to enable you to write short, simple programs using the core parts of these programming' lookup_str='' metadata={'page_number': 30.0, 'textbook_name': 'Yale-Patt_Sanjay-Patel--Intro_to_Computing_Systems'} lookup_index=0. Source: page 30 in Yale-Patt_Sanjay-Patel--Intro_to_Computing_Systems",
            "feedback_2": "Dislike",
            "custom_answer_2": "",
            "generated_answer_3": "a cell, the bit lines are held at opposite logic values, forcing the inverters to match the values on the lines and storing the value from the BIT input.",
            "context_3": "page_content='118  DRAM uses a charged capacitor to store a bit; the charge drains ov er time and must be replaced, giving rise to the quali\ufb01er \u201cdynamic.\u201d \u201cStatic\u201d thus serves only to di\ufb00erentiate memories with active logic elements from those with capacitive elements. Both types are volatile, that is , both lose all data when the power supply is removed. We consider both SRAM and DRAM in this course, bu t the details of DRAM operation are beyond our scope. 3.6.2 Static Random Access Memory Staticrandomaccessmemoryisusedforhigh-speedapplicationssu chasprocessorcachesandsomeembedded designs. As SRAM bit density\u2014the number of bits in a given chip area\u2014is signi\ufb01cantly lower than DRAM bit density, most applications with less demanding speed requirement s use DRAM. The main memory in most computers, for example, is DRAM, whereas the memory on the same chip as a processor is SRAM.12 DRAM is also unavailable when recharging its capacitors, which can be a problem for applications with stringent real-time needs. A diagram of an SRAM cell(a single bit) appears to the right. A dual-inverter loop stores the bit, and is connected to opposing BIT lines through transistors controlled by a SELECT line. The cell works as follows. When SELECT is high, the transistors connect the inverter loop to the bit lines. When writing a cell, the bit lines are held at opposite logic values, forcing the inverters to match the values on the lines and storing the value from the BITinput. When reading a cell, the bit lines are disconnected from other logic, allowing the inverters to drive the lines with their current outputs.BIT BITSELECT The value stored previously is thus copied onto the BITline as an output, and the opposite value is placed on theBITline. When SELECT is low, the transistors disconnect the inverters from the bit lines, a nd the cell holds its current value until SELECT goes high again. The actual operation of an SRAM cell is more complicated than we hav e described. For example, when writing a bit, the BITlines can temporarily connect high voltage to ground (a short). The circuit must be designed carefully to minimize the power consumed during this proc ess. When reading a bit, the BIT lines are pre-charged halfway between high-voltage and ground, a nd analog devices called sense ampli\ufb01ers are used to detect the voltage changes on the BITlines (driven by the inverter loop) as quickly as possible. These analog design issues are outside of the scope of our class. A number of cells are combined into a bit slice , as shown to the right. The labels along the bottom of the \ufb01gure are external inputs to the bit slice, and match the labels for the abstract. . . EN 4 ADDR WE DATA\u2212IN DATA\u2212OUTWED Q CS4\u2212to\u221216 decodercell 0cell cell cell 3cell 12cell 13cell 14cell 15 1 2and write logicread 4\u2212to\u221216 decoderBB memory discussed earlier. The bit slice in the \ufb01gure can be thought of as a 16-address, 1-bit-addressable memory (24\u00d71b). The cells in a bit slice share bit lines and analogread and write logic, which a ppears to the right in the \ufb01gure. Based on the ADDRinput, a decoder sets one cell\u2019s SELECT line high to enable a read or write operation to the cell. The chip select input CSdrives the enable input of the decoder, so none of the memory cells is active when chip select is low ( CS= 0), and exactly one of the memory cells is active when chip select is high (CS= 1). Actual bit slices can contain many more cells than are shown in th e \ufb01gure\u2014more cells means less extra logic per cell, but slower memory, since longer wires h ave higher capacitance. 12Chips combining both DRAM and processor logic are available , and are used by some processor manufacturers (such as IBM). Research is underway to couple such logic types more e\ufb03 ciently by building 3D stacks of chips.' lookup_str='' metadata={'page_number': 123.0, 'textbook_name': 'ECE-120-student-notes'} lookup_index=0. Source: page 123 in ECE-120-student-notes",
            "feedback_3": "Dislike",
            "custom_answer_3": ""
        },
        {
            "question": "What is a Finite State Machine?",
            "generated_answer_1": "abstract next state table",
            "context_1": "So what if I'm in the driver state, and I push the unlock button? I go to unlock. Okay, well, that's now my car is all open. So I'll get in, I'll drive somewhere, then I'll get out, and I want to lock it up. So whatever state I'm in, if I push the lock button, what should happen? Go to lock. Okay. And then last, if I get scared, doesn't matter what state I'm in, if I push the panic button, what should happen? The alarm goes off, right? Good. So that's my abstract next state table, right? So what's the problem with this? Yeah. I don't know. My table doesn't tell me. So it's incomplete, Daniel was saying, right? It doesn't tell me everything, right? So some of the transitions that I might want to know about are not defined by that table. And that's okay right now. Eventually, the system that we're going to build is going to be a digital system, and it's going to answer all the questions. So we should be careful. But this table is incomplete, meaning it doesn't specify transitions like the one Daniel asked about. It's ambiguous, right? So what happens if I push lock and panic? Which one do I go to? I can only go to one, right? And it's actually, I mean, that part is actually inconsistent, right? Because I can't go to both. Source: page  in ECE120-2016-10-10-LEC-20-slides.mp4",
            "feedback_1": "Dislike",
            "custom_answer_1": "A finate state machine is a machine that does good things.",
            "generated_answer_2": "An FSM comprises five parts: a finite set of states, a set of possible inputs, a set of possible outputs, a set of transition rules, and methods for calculating outputs.",
            "context_2": "82  3.1.3 Finite State Machines A\ufb01nite state machine (orFSM) is a model for understanding the behavior of a system by describin g the system as occupying one of a \ufb01nite set of states, moving betwe en these states in response to external inputs, and producing external outputs. In any given state, a pa rticular input may cause the FSM to move to another state; this combination is called a transition rule . An FSM comprises \ufb01ve parts: a \ufb01nite set of states, a set of possible inputs, a set of possible outputs, a set of transition rules, and methods for calculating outputs. When an FSM is implemented as a digital system, all states must be rep resented as patterns using a \ufb01xed number of bits, all inputs must be translated into bits, and all outpu ts must be translated into bits. For a digital FSM, transition rules must be complete ; in other words, given any state of the FSM, and any pattern of input bits, a transition must be de\ufb01ned from that state to another state (transitions from a state to itself, called self-loops , are acceptable). And, of course, calculation of outputs for a dig ital FSM reduces to Boolean logic expressions. In this class, we focus on clocked sync hronous FSM implementations, in which the FSM\u2019s internal state bits are stored in \ufb02ip-\ufb02ops. In this section, we introduce the tools used to describe, develop, a nd analyze implementations of FSMs with digital logic. In the next few weeks, we will show you how an FSM can se rve as the central control logic in a computer. At the same time, we will illustrate connections between F SMs and software and will make some connections with other areas of interest in ECE, such as the design and analysis of digital control systems. The table below gives a list of abstract states for a typical keyless entry system for a car. In this case, we have merely named the states rather than specifying the bit pat terns to be used for each state\u2014for this reason, we refer to them as abstract states. The description of the states in the \ufb01rst column is an optional element often included in the early design stages for an FSM, when ide ntifying the states needed for the design. A list may also include the outputs for each state. Again, in th e list below, we have speci\ufb01ed these outputs abstractly. By including outputs for each state, we implicit ly assume that outputs depend only on the state of the FSM. We discuss this assumption in more detail later in these notes (see \u201cMachine Models\u201d), but will make the assumption throughout our class. meaning state driver\u2019s door other doors alarm on vehicle locked LOCKED locked locked no driver door unlocked DRIVER unlocked locked no all doors unlocked UNLOCKED unlocked unlocked no alarm sounding ALARM locked locked yes Another tool used with FSMs is the next-state table (sometimes called a state transition table , or just astate table ), which maps the current state and input combination into the next state of the FSM. The abstract variant shown below outlines desired behavior at a high leve l, and is often ambiguous, incomplete, and even inconsistent. For example, what happens if a user pushes two buttons? What happens if they push unlock while the alarm is sounding? These questions should event ually be considered. However, we can already start to see the intended use of the design: starting f rom a locked car, a user can push \u201cunlock\u201d once to gain entry to the driver\u2019s seat, or push \u201cunlock\u201d twice to op en the car fully for passengers. To lock the car, a user can push the \u201clock\u201d button at any time. And, if a use r needs help, pressing the \u201cpanic\u201d button sets o\ufb00 an alarm. state action/input next state LOCKED push \u201cunlock\u201d DRIVER DRIVER push \u201cunlock\u201d UNLOCKED (any) push \u201clock\u201d LOCKED (any) push \u201cpanic\u201d ALARM. Source: page 87.0 in ECE-120-student-notes",
            "feedback_2": "",
            "custom_answer_2": "",
            "generated_answer_3": "It's one big combinational logic",
            "context_3": "So go build a 10 operand comparator. It's doable. You can sit down. You can write the equations out. You can solve the k-maps. Well, maybe not k-maps. But you can do a 10-input comparator. And it just spits out the biggest number. It's one big combinational logic. Then it's a very easy finite state machine. One state. Execute comparator. Done. So probably we're not going to do that. We could do that. Different design point. How we pick our components. What we did when we said, OK, we want a memory, registers, counters. How we actually pick them will affect how we design our state. So in practice, we'll go back and forth. When I actually designed this, I went back and forth. I said, well, what if I put these down? Then here's my states. Oh, but that's kind of annoying. So let me go add some more components. Now that's too complicated. So you go back and forth. But this design is all done. So I'll present it as if it were easy, but it's not. You often have to go back and forth as you see how things work. All right, so how do we pick states? So we're going to break the flowchart into pieces. Not every flowchart box is going to become a state. So I'll give you an example in a second. Well, actually, example's here. Source: page  in ECE120-2016-10-24-LEC-25-slides.mp4",
            "feedback_3": "",
            "custom_answer_3": ""
        },
        {
            "question": "asdf",
            "generated_answer_1": "a system callor aservice call",
            "context_1": "operating system to perform the task on behalf of the user program. The operatingsystem takes control of the computer, handles the request speci\ufb01ed by the TRAPinstruction, and then returns control back to the user program at location x4001.As we said at the start of this chapter, we usually refer to the request made by theuser program as asystem callor aservice call...The Trap MechanismThe trap mechanism involves several elements:1.As e to fs e r v i c er o u t i n e sexecuted on behalf of user programs by theoperating system. These are part of the operating system and start atarbitrary addresses in system space. The LC-3 was designed so that up to256 service routines can be speci\ufb01ed. Table A.2 in Appendix A contains theLC-3\u2019s current complete list of operating system service routines.2.A table of the starting addressesof these 256 service routines. This tableis stored in memory locations x0000 to x00FF. The table is referred to byvarious names by various companies. One company calls this table theSystem Control Block. Another company calls it the Trap Vector Table.Figure 9.10 shows the Trap Vector Table of the LC-3, with speci\ufb01c startingaddresses highlighted. Among the starting addresses are the one for thecharacter output service routine (memory location x0420), which is stored\nFigure.The Trap Vector Table.. Source: page 180.0 in Yale-Patt_Sanjay-Patel--Intro_to_Computing_Systems",
            "feedback_1": "Like",
            "custom_answer_1": "I liked it but this is my custom answer for number one. ",
            "generated_answer_2": "xFE00 to xFFFF do not correspond to memory locations at all",
            "context_2": "..Organization of MemoryFigure 9.2 shows the layout of the LC-3 memory.You know that the LC-3 has a 16-bit address space; ergo, memory locationsfrom x0000 to xFFFF. Locations x0000 to x2FFF are privileged memory loca-tions. They contain the various data structures and code of the operating system.They require supervisor privilege to access. They are referred to assystem space.Locations x3000 to xFDFF are unprivileged memory locations. Supervisorprivilege is not required to access these memory locations. All user programs anddata use this region of memory. The region is often referred to asuser space.Addresses xFE00 to xFFFF do not correspond to memory locations at all.That is, the last address of a memory location is xFDFF. Addresses xFE00 toxFFFF are used to identify registers that take part in input and output functionsand some special registers associated with the processor. For example, the PSRis assigned address xFFFC, and the processor\u2019s Master Control Register (MCR)is assigned address xFFFE. The bene\ufb01t of assigning addresses from the memoryaddress space will be discussed in Section 9.2.1.2. The set of addresses fromxFE00 to xFFFF is usually referred to as the I/O page since most of the addressesare used for identif in re isters that take art in in ut or out ut functions. Access\nFigure.Regions of memory.. Source: page 167.0 in Yale-Patt_Sanjay-Patel--Intro_to_Computing_Systems",
            "feedback_2": "",
            "custom_answer_2": "No like or dislike, this is for answer 2. Answer 3 is 100% EMPTY. ",
            "generated_answer_3": "the precision of the representation.",
            "context_3": "Subnormal numbers are numbers of the formN=(\u22121)S\u00d70.fraction\u00d72\u2212126We represent them with an exponent \ufb01eld of 00000000. The fraction \ufb01eld isrepresented in the same way as with normalized numbers. That is, if the expo-nent \ufb01eld contains 00000000, the exponent is\u2212126, and the signi\ufb01cant digits areobtained by starting with a leading 0, followed by a binary point, followed by the23 bits of the fraction \ufb01eld.Example.What number corresponds to the following \ufb02oating point representation?0 00000000 00001000000000000000000Answer: The leading 0 means the number is positive. The next eight bits, a zeroexponent, means the exponent is\u2212126, and the bit to the left of the binary point is 0.The last 23 bits form the number 0.00001000000000000000000, which equals 2\u22125.Thus, the number represented is 2\u22125/uni22C52\u2212126,w h i c hi s2\u2212131.Including subnormal numbers allows very, very tiny numbers to be repre-sented.Ad e t a i l e du n d e r s t a n d i n go fI E E EF l o a t i n gP o i n tA r i t h m e t i ci sw e l lb e y o n dwhat should be expected in this \ufb01rst course. Our purpose in including this sec-tion in the textbook is to at least let you know that there is, in addition to 2\u2019scomplement integers, another very important data type available in almost allISAs, which is called\ufb02oating point;i ta l l o w sv e r yl a r g ea n dv e r yt i n yn u m b e r st obe expressed at the cost of reducing the number of binary digits of precision...ASCII CodesAnother representation of information is the standard code that almost all com-puter equipment manufacturers have agreed to use for transferring charactersbetween the main computer processing unit and the input and output devices.That code is an eight-bit code referred to asASCII.A S C I Is t a n d sf o rA m e r i -can Standard Code for Information Interchange. It (ASCII) greatly simpli\ufb01es theinterface between a keyboard manufactured by one company, a computer madeby another company, and a monitor made by a third company.Each key on the keyboard is identi\ufb01ed by its unique ASCII code. So, forexample, the digit 3 is represented as 00110011, the digit 2 is 00110010, thelowercaseeis 01100101, and the ENTER key is 00001101. The entire set ofeight-bit ASCII codes is listed in Figure E.2 of Appendix E. When you type a keyon the keyboard, the corresponding eight-bit code is stored and made available tothe computer. Where it is stored and how it gets into the computer are discussedin Chapter 9.Most keys are associated with more than one code. For example, the ASCIIcode for the letterEis 01000101, and the ASCII code for the lettereis 01100101.. Source: page 50.0 in Yale-Patt_Sanjay-Patel--Intro_to_Computing_Systems",
            "feedback_3": "",
            "custom_answer_3": ""
        }
    ]
}