CS 2318 (Assembly Language) by Lee S. Koh
Exam 1 Study Guide 

■ General


● When:


    SectionDateStart Time


    25102-20-2025 (Thursday)11:00 am


    255 & 256
02-20-2025 (Thursday)06:30 pm

● Duration: 1 hour 20 minutes.

● Questions can be on anything covered up to the most recent lecture (on 02/18/25).


► That means the relevant lecture notes are
 001 BigPictures
 001 BigPictures_Sup01 - focus on catching the "big piture" (not details of any particular aspects)
 001 BigPictures_Sup02 - focus on catching the "big piture" (not details of any particular aspects)
 001 BigPictures_Sup03 - focus on catching the "big piture" (not details of any particular aspects)
 001a MotivationPushAndRealityCheck
 002 DigitalInfoRepresentation01
 002_ DigitalDataRepresentationPanoramically
 002__ DistinctPatternsWithHybridDigits
 003 DigitalInfoRepresentation02
 003a SupplementaryLectureNote(forReplacementClass)
 004 DigitalInfoRepresentation03
 004a SupplementaryLectureNote(forReplacementClassInThePast)
 005 DigitalInfoRepresentation04
 005 DigitalInfoRepresentation04Sup01(Unicode and UTF-8)
 005_ PertinentBinaryEncodingFormulas
 005a NotesOnBitwiseOperations

● Test will be closed books / notes / online-resources / discussion and no calculating devices of any kind are allowed.


► All allowed reference material (such as IEEE 754 signed real number encoding/decoding schematic and ASCII chart) will be provided as part of the exam.


► All electronics off during the exam. (In particular: no calculators of any kind allowed.)

■ Checklist of (most if not all) the things you are expected to know


● Where and how assembly language fits in, relative to:


► Virtual machine layers (abstraction in hardware).



○ Instruction Set Architecture (ISA) as interface between hardware and software, in particular.




♯ Typically specifies instruction set, (general purpose) registers, data types and addressing modes.





♦
 instruction: primitive operation (task) processor supports (e.g., add) - each has 2 main parts in opcode (operation code) and operands.






⁃⁃ First look at CISC (complex instruction set computers) and RISC (reduced instruction set computers).





♦
 register: fastest kind of storage device (located on processor chip) of the typical computer.






⁃⁃ general-purpose registers: those (assembly-language) programmers get to use to write programs.






⁃⁃ 2 special-purpose registers of note: program counter (PC) and instruction register (IR).
(The key roles PC and IR play relative to a first look at the fetch-decode-execute cycle involved in program execution.)





♦
 data type: set of representable values + set of relevant operations (e.g., int).





♦
 addressing mode: way of specifying the location(s) of operand(s) involved in an instruction - each operand may be a soure operand or a destination operand.




♯ But not implementation.


► Other programming languages (espcially higher level ones).



○ 1GL, 2GL, 3GL, 4GL, . . .: machine language is 1GL, assembly language is 2GL and high-level language is 3GL.



○ Reflected in typical translation hierarchy for C: compiler --> assembler --> linker --> loader.




♯ compiler does "high-level language → assembly language" translation.




♯ assembler does "assembly language → machine language" translation.

● In terms of lines of code needed to express a computation, how is assembly language typically different compared to high-level languages.


► To accomplish the same thing, assembly language typically requies more lines of code than high-level language.

● Advantages/disadvantages, common application areas and truths and half-truths of assembly language.


► Undeniable truth: not portable (e.g.: assembly language program written to run on MIPS will not run on INTEL).

● Meaning of digital and digital system.

● Characteristics/implications/consequences/. . . of/for being digital.


► Discrete and finite (as opposed to continuous and infinite that apply to analog).


► sn # of (distinct/unique) states associated with digital system (s = # of digital variations, n = # of digits involved).


► s1 х s2 х . . . х sn # of (distinct/unique) states associated with hybrid digital system (s1 = # of digital variations of digit 1, . . ., sn = # of digital variations of digit n).


► Partial (selective/discrete) represention to deal with digital-reality mismatch often encountered.

● Present-day's predominate finite-state device.


► Transistor - electronic - switching (not regulating) circuit - 2-state (not 3-or-more-state) - binary - why.

● How many unique values (or range of zero-and-higher whole numbers) a given set of finite-state devices (i.e., bits or "tit"s or "qit"s etc.) is able to represent.

● Minimum number of bits (or "tit"s or "qit"s etc.) required to represent a given number of unique values (or range of zero-and-higher whole numbers).

● How bits (or "tit"s or "qit"s etc.) can be used to represent anything.


► Can encode/represent anything with numbers.



○ (Each of us is treated/represented as numbers often enough!)


► Can represent any finite number of numbers if finite-state devices are available in sufficient number.

● What 2 basic strategies for binary encoding of set of items (such as set of values) are.


► Base it on mathematical formula.


► Base it on assigned item-pattern mapping - typically crafted in some way (and not arbitrarily).

● Know about ASCII code and Unicode.


► In particular: how is Unicode different than ASCII code, and why (-> globalization / internationalization).


► For backward compatibility, the first 128 Unicode characters point to ASCII characters.



○ (some allude to this by saying that ASCII is a subset of Unicode)

● ASCII character encoding in more detail.


► Some key characteristics:



○ The positive whole number the byte (encoding a character) evaluates to is the ASCII value of the character.



○ Characters representing digits come before (have lower ASCII values) than letters (alphabets) and appear consecutively in increasing order of ASCII value.



○ The ASCII value of the character representing 0 ('0') is not 0.




♯ The character with ASCII value 0 is the null character ('\0') that is used as the null terminator in C-strings.



○ Uppercase letters (alphabets) come before (have lower ASCII values) than lowercase letters (alphabets) and appear consecutively in increasing order of ASCII value.



○ Lowercase letters (alphabets) come after (have higher ASCII values) than uppercase letters (alphabets) and appear consecutively in increasing order of ASCII value.



○ An uppercase letter (alphabet) and it's lowercase counterpart appear in the same column on the ASCII chart.




♯ Their bit patterns differ by only 1 bit (the 5th bit, with the least significant bit being the 0th bit).




♯ 'a' does not come immediately after 'Z' (but there's a 6-character gap between them) on the ASCII chart.


► In particular: understand and know how to apply the following (in part or in whole).



ASCII character chart

● How positional numbers are defined for unsigned whole numbers and fractions and how to use the definition in evaluations.


► (Our scope confined to the usual way the numbers are represented that we looked at, i.e., representations based on radix polynomials.)

● What Horner's scheme is and where and how it can be used to effect efficient evaluations.


► The double-and-add method for evaluating unsigned binary numbers.


► Extended use in other mathematically similar settings: triple-and-add, quadruple-and-add, . . . for ternary (base-3), quarternary (base-4), . . . numbers.

● How to convert decimal whole numbers to binary using the repeated subtraction and repeated division methods.


► Similarly for converting decimal whole numbers to ternary, quarternary, . . .

● How to convert decimal fractions to binary using the repeated multiplication method.

● How to quickly translate a hex digit into the equivalent 4 binary digits and vice versa.

● How to convert from binary (both whole numbers and unsigned real numbers) to hex and hex to binary.

● Know the rules for and use them to perform binary addition.

● The 4 different methods (as discussed in class) for representing signed whole numbers, their characteristics, and some key reasons for the predominant use of 2's complement.


► SM, 1C, 2C, Bias (Excess)

● The polynomial representation for a 2's complement number and the associated Horner's scheme for evaluating the decimal equivalent of a 2's complement number.

● How to quickly find the 2's complement of a binary number, i.e., without having to first find the 1's complement and then add 1.

● What overflow is.


► Know the key advantage 2C has (over SM and 1C) --> main reason most modern computers use 2C to represent signed whole numbers.



○ Same way (thus device) used to "add unsigned whole numbers" and "add signed whole numbers" --> just have to detect overflow differently.

● How to detect overflow when performing addition involving unsigned numbers and when involving 2's complement numbers


► By examining the state(s) of certain bit(s) in 1 or 2 positions.


► List of observations (note that each is in terms of the state(s) of certain bit(s) in 1 or 2 positions -- something that can be easily made in hardware):



- carry-out is 0 when bits at most-significant-bit position are added.
- carry-out is 1 when bits at most-significant-bit position are added.
- addends have opposite signs.
- addends are both positive, sum is positive.
- addends are both positive, sum is negative.
- addends are both negative, sum is positive.
- addends are both negative, sum is negative.
- carry-in and carry-out at most-significant-bit position are the same.
- carry-in and carry-out at most-significant-bit position are not the same.

● How to quickly arrive at the range of 2's complement numbers a given number of bit can represent (in terms of powers of 2).


► Range for n-bits: [  -2n-1  ,  2n-1 - 1  ] 

● How to derive ballpark ideas about 2's complement numbers (comparative ideas about them: negative or positive and relatively more negative or positive).

● Know about lengthening/shortening of binary whole numbers (unsigned or 2's complement) and when the operations are needed/appropriate.


► In particular: zero-extension and sign-extension.


► (Note that "more compact (shorthand) representation in hex" of the binary whole numbers involved may be called for.)

● How oddness/evenness (in general, divisibility by some power of 2) can be quickly determined for signed/unsigned whole numbers represented in binary and hex.

● Know the key features of IEEE 754-1985 single-precision and double-precision formats.


► Sign bit, biased exponent, fraction (or significand or mantissa) and hidden bit.

● How to encode and decode a signed floating-point number in IEEE 754-1985 single-precision and double-precision formats.


► Understand and know how to apply the following (in part or in whole):



IEEE 754 Encode-Decode Helper Formula and Diagram

● How to derive ballpark ideas about signed floating-point number in IEEE 754-1985 (comparative ideas about them: negative or positive and relatively more negative or positive).

( and whatever bitwise operations items below we get to cover up to and including the 02/18/25 lectures )

● Know about bitwise operations, what they are useful for, and how to put them to use.


► What bit shifting is and how it can be useful.



○ Logical left shift, logical right shift, arithmetic right shift.



○ Efficient multiplication and division by powers of 2 for signed/unsigned numbers (and unsigned floating-point numbers) represented in binary.




♯ How, and under what provisions (for results to be valid).



○ Simply to bring certain bit(s) to certain desired position(s).


► What binary bitwise operation(s) and mask(s) to use to attain certain effects (setting/clearing/toggling/complementing/extracting/isolating/... of bit(s)).



○

Bitwise-AND

 -->

1 shows, 0 hides (behind 0)




(bit clearing with 0)

Bitwise-OR

 -->

0 shows, 1 hides (behind 1)




(bit setting with 1)

Bitwise-XOR

 -->

0 shows, 1 hides (behind "the reverse of actual")

(bit toggling with 1)



○ What combination of operation and mask to use to go from what's given to what's desired.


► XOR intrigue:



○ Same polarity gives 0, different polarity gives 1.



○ XOR a bit pattern P with itself makes P all 0's (clears P).

■ Other


● Use Assignment 1 (all 3 parts) as part of your preparation.


► Caveat: You should definitely not take it that the exam will only cover material involved in Assignment 1.



(In particular: Expect significant number of conceptual questions, noting that pretty much all assignments have been quantitative.)

● Take advantage of relevant drills and challenges exercises posted on the class homepage (under Drills And Challenges).


► DaC201 DigitalDataRepresentation (in particular).


► DaC202 BitwiseOperationsAndMasking.

● You may want to check out sample past exam questions posted on the class homepage (under Other Resources).


► You should not however, expect the questions to be identical in number, kind, topic coverage, etc.


► Notion very ill-advised to harbor:
     I take it I will do well in current exams if I can do the sample past exam questions well.


► You should not have to worry about questions being written on topics we have not (or not yet) covered; some such questions may appear as sample past questions because the associated topics were appropriate at that time.

● Do the following if you are eligible and intend to use extended time accommodation:


► Follow proper procedure to request taking the exam at the ATSD.



○You typically need to do the request at least a certain number of (non-weekend?) hours in advance.



○The exam date of your request should be the same as the (regularly) scheduled date of the exam.



○The exam start time of your request should be closest to the (regularly) scheduled start time of the exam.