FINAL REVIEW Slides "Weeks 01 through 04" Flashcards
What is professor Adams’ Email
gba@purdue.edu
What is software?
Description of a computation expressed in a programming language, any necessary data, and documentation
What executes software?
An interpreter: A system that directly executes instructions expressed in a programming language
what are compiled programming languages?
high-level programming languages without an interpreter are compiled
memorize and look at the diagram of compiling for C (Figure 4.6, slide 21)
ok daddy
which step in the figure passes C language statements from input to output unchanged?
preprocessor
_____ code is interpreted by a machine
object
Where was the germanium crystal made?
Purdue
Today electronic computers are built from _____ elements
Silicon (Si)
Basic Capabilities an interpreter should have:
-Accept input
-Store values (include the memory function)
-Update / change existing values (variables)
-Compute (perform functions on value(s))
-Create output
Harvard Architecutre:
Had two separate memories, one for instruction memory and one for data memory. Also had processor (circuit to carry out computation) and input/output
Von Neumann Architecture:
One memory for both program and data, also had processor and I/O. Design was more flexible, and hence, economical, however less secure than Harvard since there was only 1 memory.
How many distinct bands in volatge?
2
4 parts of digital logic signal voltage waveform
1) low level 2) rising edge 3) high level 4) falling edge
how many wires does a k-bit bit string have?
k wires
a collection of k wires carrying the k bits of a k bit string
bus
how many distinct k-bit strings are there?
2^k (Product Rule of combinatorics)
Kibi
2^10
Mebi
2^20
Gibi
2^30
Tebi
2^40
unsigned integer, base 2, weighted positional
Add together powers of 2 if they’re “on” (1)
sign magnitude integer representation
leftmost bit represents sign: 0 = +, 1 = -, remaining bits are magnitude as usual (However, has + and - 0
two’s complement integers
Weighted, but MSB weight is negative:
-2^(n-1), + 2^(n-2), + …, + 2^1, + 2^0
Given a bit string A, how do you obtain -A using 2’s comp?
flip bits and add 1
sign extension:
drag the bits out to go from 4 bit to 8 bit representation (in 2’s comp)
big endian:
most significant bye, “Big” byte, comes first (placed in lowest-numbered memory location), in MSB to LSB order
Little endian:
the reverse of big endian; least significant byte, “little” byte, placed in lowest address followed from remaining bytes in LSB to MSB order
True or false: Order of bits within a byte is NEVER changed for big / little endian
True
what do you need to know to define floating point?
Number of bits, sizes of fields within the bit string, encoding used for each field
precision:
resolution of a representation system
-defined as the minimum difference between any two representations
-precision of 32-bit integers is +/-1
range:
the bounding number pair (smallest, largest) of a given representation
- for 32-bit unsigned integers range is (0, 2^32 - 1)
32 bit IEEE Floating Point Standard 754 has:
32 bits:
1 sign bit (31),
8 exponent bits (23-30)
23 bit mantissa (0-22)
64 bit IEEE Floating Point Standard 754 has:
64 bits:
1 sign bit (63)
11 exponent bits (52 - 62)
52 bit mantissa (0-51)
The IEEE 754 representation fields are sign, ____ exponent, and mantissa
biased
Normalized mantissa has ___ significant digit(s) to the left of the radix point
One
a k-bit pointer has how many locations in memory?
2^k locations
how many bits would a register be that’s formed from four 1-bit latches
4-bits
a decoder is a circuit with:
n input wires with voltages to encode a memory address, A, from a set of 2^n memory addresses
2^n output wires, one for each available memory address
selects 1 of 2_n k-bit input buses to connect to the k-bit output bus
multiplexer, used to read (copy) bits from a memory location
connects the k-bit input bus to 1 of the 2^n k-bit output buses
demultiplexer, used to write bits into a memory locations
transporting a bit string from one of many storage locations to a processor circuit is called a ____
fetch
clock rate upper bound set by _____
worst case circuit propagation delay
CPU Time =
(Instructions / Program) * (Clock cycles / Instructions) * (seconds / clock cycle) = (seconds / program)
True or false: When last instruction is executed, computer keeps running
True; need an idle loop or else computer will crash without any instructions
what is the process called that starts the fetch / execute cycle?
bootstrapping
What are the machine instruction fields?
Opcode | operands 1, 2, … | Results
opcode is…
selects ALU result to use, aka what to do
operands are…
input to ALU, see opcode to determine how many (if any) are needed for that opcode
results are…
a pointer to a storage location, also optional depending on the opcode used
2 choices for machine instruction bit string length:
fixed length and variable length
variable length machine instruction:
concatenate fields with no limitations on number of or sized of the fields
fixed length machine instruction:
encode all instructions in a fixed number of bytes
advantages / disadvantages of variable length machine instruction
Adv:
-unlimited capability of ISA, just add bytes
-can select short encodings for commonly occurring instructions to reduce program size
Disadv:
-hard to prevent Marketing from adding to ISA
-instruction decryption is complex: how many bytes to examine, what do they say?
-makes hardware slower
advantaged / disadvantages of fixed length machine instruction
adv:
-easy to quickly fetch a fixed size object from memory
-instruction decryption is fairly simple
-ISA criteria are largely technical because cannot add byres
Disadv:
-hard to expand ISA
True / False: Operands and Result fields drive up instruction length
True, 3 memory pointer fields, memory locations are 1 byte in size
What do compilers do?
Translate HLL to target language
Hiding underlying details
Abstraction
Operation result is greater than max representable value
Overflow
Result is less than smallest representable value
Underflow
Set of operations chosen
ISA
