Chapter 2: Data Manipulation

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Chapter 2:

Data Manipulation

Computer Science: An Overview Twelfth Edition

by

J. Glenn Brookshear

Dennis Brylow

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Chapter 2: Data Manipulation

• 2.1 Computer Architecture

• 2.2 Machine Language

• 2.3 Program Execution

• 2.4 Arithmetic/Logic Instructions

• 2.5 Communicating with Other Devices

• 2.6 Program Data Manipulation

• 2.7 Other Architectures

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Computer Architecture

• Central Processing Unit (CPU) or processor

– Arithmetic/Logic unit versus Control unit – Registers

• General purpose

• Special purpose

• Bus

• Motherboard

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Figure 2.1 CPU and main memory

connected via a bus

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Stored Program Concept

A program can be encoded as bit patterns

and stored in main memory. From there,

the CPU can then extract the instructions

and execute them. In turn, the program to

be executed can be altered easily.

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Terminology

• Machine instruction: An instruction (or command) encoded as a bit pattern

recognizable by the CPU

• Machine language: The set of all

instructions recognized by a machine

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Machine Language Philosophies

• Reduced Instruction Set Computing (RISC)

– Few, simple, efficient, and fast instructions

– Examples: PowerPC from Apple/IBM/Motorola and ARM

• Complex Instruction Set Computing (CISC)

– Many, convenient, and powerful instructions

– Example: Intel

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Machine Instruction Types

• Data Transfer: copy data from one location to another

• Arithmetic/Logic: use existing bit patterns to compute a new bit patterns

• Control: direct the execution of the

program

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Figure 2.2 Adding values stored in

memory

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Figure 2.3 Dividing values stored in

memory

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Figure 2.4 The architecture of the

machine described in Appendix C

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Parts of a Machine Instruction

• Op-code: Specifies which operation to execute

• Operand: Gives more detailed information about the operation

– Interpretation of operand varies depending on

op-code

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Figure 2.5 The composition of an instruction for the machine in

Appendix C

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Figure 2.6 Decoding the instruction

35A7

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Figure 2.7 An encoded version of the

instructions in Figure 2.2

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Program Execution

• Controlled by two special-purpose registers

– Program counter: address of next instruction – Instruction register: current instruction

• Machine Cycle

– Fetch

– Decode

– Execute

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Figure 2.8 The machine cycle

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Figure 2.9 Decoding the instruction

B258

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Figure 2.10 The program from Figure 2.7

stored in main memory ready for execution

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Figure 2.11 Performing the fetch step

of the machine cycle

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Figure 2.11 Performing the fetch step

of the machine cycle (continued)

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Arithmetic/Logic Operations

• Logic: AND, OR, XOR

– Masking

• Rotate and Shift: circular shift, logical shift, arithmetic shift

• Arithmetic: add, subtract, multiply, divide

– Precise action depends on how the values are encoded (two’s complement versus floating-

point).

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Figure 2.12 Rotating the bit pattern

65 (hexadecimal) one bit to the right

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Communicating with Other Devices

• Controller: An intermediary apparatus that

handles communication between the computer and a device

– Specialized controllers for each type of device – General purpose controllers (USB and

FireWire)

• Port: The point at which a device connects to a computer

• Memory-mapped I/O: CPU communicates with

peripheral devices as though they were memory

cells

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Figure 2.13 Controllers attached to a

machine’s bus

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Figure 2.14 A conceptual representation

of memory-mapped I/O

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Communicating with Other Devices

(continued)

• Direct memory access (DMA): Main memory access by a controller over the bus

• Von Neumann Bottleneck: Insufficient bus speed impedes performance

• Handshaking: The process of

coordinating the transfer of data between

components

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Communicating with Other Devices

(continued)

• Parallel Communication: Several communication paths transfer bits simultaneously.

• Serial Communication: Bits are

transferred one after the other over a

single communication path.

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Data Communication Rates

• Measurement units

– Bps: Bits per second

– Kbps: Kilo-bps (1,000 bps)

– Mbps: Mega-bps (1,000,000 bps)

– Gbps: Giga-bps (1,000,000,000 bps)

• Bandwidth: Maximum available rate

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Programming Data Manipulation

• Programing languages shields users from details of the machine:

– A single Python statement might map to one, tens, or hundreds of machine instructions

– Programmer does not need to know if the processor is RISC or CISC

– Assigning variables surely involves LOAD, STORE, and MOVE op-codes

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Bitwise Problems as Python Code

print(bin(0b10011010 & 0b11001001))

# Prints '0b10001000'

print(bin(0b10011010 | 0b11001001))

# Prints '0b11011011'

print(bin(0b10011010 ^ 0b11001001))

# Prints '0b1010011'

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Control Structures

• If statement:

if (water_temp > 140):

print('Bath water too hot!')

• While statement:

while (n < 10):

print(n) n = n + 1

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Functions

• Function: A name for a series of

operations that should be performed on the given parameter or parameters

• Function call: Appearance of a function in an expression or statement

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x = 1034 y = 1056 z = 2078

biggest = max(x, y, z)

print(biggest) # Prints '2078'

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Functions (continued)

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• Argument Value: A value plugged into a parameter

• Fruitful functions return a value

• void functions, or procedures, do not return a value

sideA = 3.0 sideB = 4.0

# Calculate third side via Pythagorean Theorem hypotenuse = math.sqrt(sideA2 + sideB2)

print(hypotenuse)

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Input / Output

# Calculates the hypotenuse of a right triangle import math

# Inputting the side lengths, first try sideA = int(input('Length of side A? ')) sideB = int(input('Length of side B? '))

# Calculate third side via Pythagorean Theorem hypotenuse = math.sqrt(sideA2 + sideB2)

print(hypotenuse)

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Marathon Training Assistant

# Marathon training assistant.

import math

# This function converts a number of minutes and

# seconds into just seconds.

def total_seconds(min, sec):

return min * 60 + sec

# This function calculates a speed in miles per hour given

# a time (in seconds) to run a single mile.

def speed(time):

return 3600 / time

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Marathon Training Assistant (continued)

# Prompt user for pace and mileage.

pace_minutes = int(input('Minutes per mile? ')) pace_seconds = int(input('Seconds per mile? ')) miles = int(input('Total miles? '))

# Calculate and print speed.

mph = speed(total_seconds(pace_minutes, pace_seconds)) print('Your speed is ' + str(mph) + ' mph')

# Calculate elapsed time for planned workout.

total = miles * total_seconds(pace_minutes, pace_seconds) elapsed_minutes = total // 60

elapsed_seconds = total % 60

print('Your elapsed time is ' + str(elapsed_minutes) + ' mins ' + str(elapsed_seconds) + ' secs')

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Figure 2.15 Example Marathon Training Data

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Time Per Mile Total Elapsed Time

Minutes Seconds Miles Speed (mph) Minutes Seconds

9 14 5 6.49819494584 46 10

8 0 3 7.5 24 0

7 45 6 7.74193548387 46 30

7 25 1 8.08988764044 7 25

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Other Architectures

• Technologies to increase throughput:

– Pipelining: Overlap steps of the machine cycle – Parallel Processing: Use multiple processors

simultaneously

• SISD: No parallel processing

• MIMD: Different programs, different data

• SIMD: Same program, different data