20191206 "Introduction to information security professionals," the fourth week of learning summary

First, the "Introduction to Computer Science"

Chapter IV - gate and circuit

(A) Electrical and Computer

First, there must be an electrical circuit ( Circuit ), is a gate circuit ( Gate ) composed implement the specified logical functions, you can perform more complex tasks. Door apparatus to perform basic operations on the electrical signal, or receiving a plurality of inputs, generating an output. Notation described and three circuits: boolean ( Boolean algebra ) expression, a logical block diagram ( Logic Diagram ), the truth table ( Truth Table )

 

(B) the door

Six kinds of doors:

AND gate ( and ) the whole truth to be true  A * B

NAND ( Not ) reversed authenticity A '

OR gate ( or ,) before the whole false false A + B

Exclusive OR gate ( XOR ) is true different A ring plus B

NAND gate ( NAND ) and Not + (A * B) '

NOR gate ( NOR ) or Not + (A + B) '

 

(C) of the door structure

It is used to control the current gate. Transistors ( Transistor ) is used to achieve this function of the underlying hardware, the transistor material, a semiconductor ( Semiconductor ). A transistor; as a wire or a resistor, which is determined by a specific input level.

Input and output transistors: a NAND gate itself, a ground, 0 ungrounded

NAND gate: in series, both inputs are 1 , was ground output 0 and the door: There is a 0 , is 0

NOR gate: in parallel with an input 1 is grounded, a source electrode was short-circuited, the output of 0    or door: There is a 1 , that 1

 

(D) Circuit

Circuit may be divided into two categories, one category is combining circuit ( Combination Circuit ) (the output is determined only by the input value) is another timing circuit ( Sequential Circuit ) circuit output is a function of the current state of the circuit and the input value.

Combining circuit: the output of a gate as the other input gate circuits can be combined into a door.

Equivalence - in line with the distribution ratio

Morgan's law (AB) '= A' + B '(A + B)' = A'B '

Adders ( Adder ): adding circuit for performing binary.

Half adder ( Half Adder ): two-digit calculating circuit and the right and generates a carry. Our calculation is the actual output of two. Only calculates half adder input bits are binary

Full adder ( Full Adder ): calculated two-digit and, taking into account the carry input of the circuit.

Multiplexer :( Multiplexer ) is a general circuit generating a single output signal, the output value is equal to one of a plurality of values of the input circuit. The multiplexer input select signal or signals as selection control lines select which input signal as an output signal.

Demultiplexer: perform the inverse operation of the multiplexer.

The storage circuit ( the SR latch)

IC ( Integrated Circuit ) (Chip Chip ): a plurality of gate embedded in silicon.

CPU is a high-level circuit having an input line and an output line.

 

Chapter V - calculation means

Von Neumann architecture: means for processing information independent of the means for storing information

The concept (a) storing programs

Five components: a memory unit, an arithmetic logic unit, an input unit, an output unit, a control unit

Memory addressability: in each addressable memory location to store the number of bits of the address.

An arithmetic logic unit: the ALU performs the basic arithmetic and logic operations

ALU a small number of special storage units: a register for storing intermediate values or special data

The input unit: INPUT Unit output unit output unit

Control unit: in charge of "Reading execution" cycle, is the organizational strength in the computer.

Instruction register ( the IR ) holds the current instruction register. ,

Program counter ( the PC register address of the next instruction) to be executed is stored.

A central processing unit ( the CPU combinations of arithmetic logic unit and a control unit:)

Bus: carry three kinds of information, address, data and control information.

Bus width ( Bus width ) parallel bits transmitted on the bus

Cache ( Cache Memory ) storing frequently used data in a small high-speed memory

Pipeline ( PIPELINING ) A command into smaller steps may be performed in the overlap technique

Motherboard ( Motherboard ) main wire board

Read - execution cycle

RAM / ROM

Secondary storage devices: disk drive, the track ( Track ) sector ( a SECTOR ) Block ( Block ) seek ( Seek Time ) latency ( Latency ) access time ( Access Time ): seek time + latency, the transmission rate ( Transfer Rate )

 

 

(B) Embedded Systems

Embedded Systems: The concept is vague, contains in addition to a desktop PC all things. The tendency is equivalent to the system hardware.

(C) parallel structure

The general form of parallel computing: Bite level, instruction level, the data level, task level

Sync ( Synchronous Processing ): The multi-processor applied to the plurality of data sets with a program.

Shared Memory Parallel Processor ( Shared Memory Parallel Processor ): a plurality of processors share memory where the entire

Digital Divide

 

Second, the "self-study is a craft."

Chapter V strings

1. Character, the code conversion table the ord (), CHR ()
2. Converting between strings and numerical STR () a float () int () INPUT ()
3. Escape: \ "also called a caret"
4. String operators: + and function the same space, so that the two strings can be spliced together, * the like repetition, I judge true or false, returns a Boolean value
5. String index string is an ordered container. Indexing operator []
6. Built-in functions for manipulating strings the ord , INPUT , int , a float , len , Print
7. For string processing method invocation str needs . This symbol.
8. Case Processing: Str.upper () str.lower () str.swapcase () str.casefold () str.capitalize () str.title ()
9. Search and replace str .count () str.find. () Str.rfind () str.index ()

Str.startswith（） str.endswith（）str.replace（）str.expandtabs（）

1. Removal of the child character str.strip () str.lstrip () str.rstrip ()
2. Split string STR .partition () str.splitlines () str.split ()
3. String concatenation str.join ()
4. String layout str.center () str.ljust () str.rjust ()
5. Format string str.foramt ()
6. String attribute str.isalnum () str.isalpha () str.isdecimal () str.isdelight () str.isnumeric ()

Chapter VI data container

1, iteration ( the iterate ) data elements of the container can be iterative. The container elements can be accessed individually, there is an operator in Range ()

2, the list of list ordered type of container, the generated list mode a_list = [] b _ list = [1,2,3] a_list.append ()

Magical method list comprehension

3, a list of operators splice +   copy: *; logic operation: in, Not in, comparison operators

4, according to the index to extract a list of elements

5, a list of available built-in functions .len .max .min

6, Method, , tuples, sets, dictionaries did not look carefully. .

Chapter VII file

1, create a file built-in function Open ()

2, delete the file calls the os module

3, read and write files f.write () reached, f.read () f.readline ()

4, With statement block

 

ISSUES

1. How to make python does not automatically shut down after running interface
2. ord What shorthand?
3. \ n specification writing a new line