david touches kids

next

Execute the next line of code, pausing once it is completed. If the line contained a function call, run the whole function

display expression

Show the value of expression whenever the program pauses execution

finish

Complete the current function you are in and go back to where this function was called

up

Move up one level on the call stack

print expression

Show the value of expression once

watch expression

Cause the program to pause execution whenever the value of expression changes

bt

Show the current call stack

down

Move down level on the call stack

step

Execute the next line of code, pausing once it is completed. If the line contained a function call, pause at the beginning of the called function

continue

Resume execution of the program until it hits the next breakpoint or reaches the end of the program

run

Start/restart execution of the program

break location

Cause the debugger to pause the program when it reaches the specified location

Nibble

4 bits

Byte

8 bits

S unique states

log2(s) bits

Int

4 bytes

Short

2 bytes

Char

1 byte

Float

4 bytes

Double

8 bytes

Logical Right Shift

unsigned int, char, short

Arithmetic Right Shift

int, char, short

Little Endian

• The least significant byte of a word is stored at the lowest part of an address(backwards)

Big Endian

• The most significant byte of a word is stored at the lowest part of an address(forwards)

One big Chunk

Advantages: Quick to access, works good with caches since elements next to each other

Disadvantages: Must know size of arrays at compile times, must specify size of dimensions

Array of Arrays

Advantages: Can have ragged arrays,don’t need to know size of array ahead of time

Disadvantages: Requires more space to store pointers, can be slower to access, rows aren’t adjacent

Global variables

Stored in order of appearance so the first global will have the lowest address

Arguments

Stored in order of appearance so the first argument will have the lowest address

Locals

Stored in reverse order of appearance so the last local will have the lowest address

Compiler Guard

Many protections come from computer instead of hardware, compiler refuses access of private variables, nothing in hardware protects it.

Row Major

K= i * N + j

Column Major

K = j * M + i

Major components of computer

Hardware, Low level Software(operation system, system calls)

Issues with Hardware

Programs run on one CPU will not run on another

Issues with Software

System calls will be different for different operating systems.

CPU

Executions instructions of program

Memory

Store’s program’s instructions and data

I/O Devices

Allows computer to interact with outside world(hard drive, monitor, mouse,keyboard)

System Bus

Wires that connect components so they can communicate, nothing stored, include control, address, and data bus

RAM

Takes same amount of time to access element regardless of where it is, volatile, where programs are stored when running

ROM

Nonvoltaile, when powered off stuff stays, system bios stored here

Control Bus

Used to send control signals such as read and write

Address Bus

use to send address you want to read from or write to

Data Bus

IF control bus says read: data bus will contain value read from memory at value sent to address bus, IF control says write: data bus will contain the value you want to write to memory

ALU

performs operations( addition, subtraction, bitwise AND) ,etc, does not store anything but calculations

Data Registers

small fast memory inside of CPU used to store data and results of operations

PC(Program Counter)

Holds address of instruction currently being executed

Instruction Register(IR)

Holds instructions being executed

ESP

Stack pointer, points to top of program’s stack

MAR(memory address register)

register connecting CPU to Address bus

MDR(memory data register)

register connecting CPU to data bus

EFlags

Stores various bits of data about the state of the program)(ex: What mode are we on? was the last digit 0?)

CPU Cycle

Fetch, Decode, Execute, Write(FDEW)

CPU Time

number of instructions/ program * clock cycles/ instruction * time/ clock cycles

Wall Time

Amount of time it takes for your program to finish, usually greater than CPU time because of delays

Parallelism

multiple operations at the same time

-Message passing: Processes explicitly send messages to one another

-Shared memory: Processes share information implicitly through shared memory

Pipelining

Breaking sequence into multiple stages and doing each stage to different things, limit to time of slowest stage(ex. washing clothes, cpu cycle(4x))