Newline characters

Recall the last time

• The number system can be transformed into

  • bin(n) You can convert numbers into 2 Base number
  • hex(n) You can convert numbers into 16 Base number
  • int(n) You can convert numbers into 10 Base number

• Encoding and decoding can be transformed into

  • encode code
  • decode decode

• ASCII Code table range

  • 0x41-0x5A This range is Big Write letters
  • 0x61-0x7A This range is Small Write letters

  • 0x30-0x39 This range is Numbers

    • The coding of numbers minus 0x30 Just get the number itself
  • 0x20-0x7F There are various symbols between
  • 0x00-0x1F What is the thing between ？

File encoding

• Write a document

  • write down abcd
  • use :%!xxd
  • :%!xxd -r Change back

• You can see that the file is in 2 Base number Mode stored

  • 0x61 - a
  • 0x62 - b
  • 0x63 - c
  • 0x64 - d
• The one in the back 0a What is it?
• We have to go back to the beginning

Back to the original

• Let's go back to the beginning
• Previously introduced c The first program of language

• be aware hello world hinder \n Why? ？

  • be aware hello world hinder \n Why? ？
  • Pay special attention to the direction of the slash
  • In this direction \ It's called a backslash
  • On the return
• that \n What is it ？？

Output "\n"

# Output \n
print("\n")
# direct print
print()
# Look at the ordinal number
ord("\n")
# Check the hexadecimal serial number
hex(ord("\n"))

• Let's just output him
• Seems to have changed two That's ok
• If not \n Words , Change only One That's ok

• \n As a whole as a character

  • The serial number is (10)_{10 Base number}
  • That is to say (0x0A)_{16 Base number}

Find a place

• 10 It's hexadecimal 0x0A
• This value is in ascii The code table means LF
• What do you mean by that? ？

Search for

• Search for \n The result is like this

  • LF signify Line Feed Hello, Yixing ？
• Then I can really use this \n Change your career ？

# Output string with \n
print("Hello\nWorld")

• The line change is successful ！

A few more

# Output string with \n
print("He\nllo\nWor\nld")

• Obviously this \n It's just a line feed

  • There is a... In the string \n It means you need to change 1 That's ok
  • His English is Line Feed
  • It means New 1 That's ok
  • This thing is actually better than ascii It has a long history
  • From the era of typewriters

• At the beginning, paragraphs are divided by outputting spaces and then wrapping

  • Ever since I had this
  • One key has a new line
  • therefore LineFeed Very efficient

The inverse

# Output ascii The value is 10 The characters of
chr(10)
# Put this character in print It outputs
print("hello"+chr(10)+"world")

Go back to history

• Earliest c Language Medium \n From what ？

  • From B Language
  • B Language It was first developed by rich and Thompson unix Language
  • He runs in bell laboratory Of PDP-8 On
  • 1969 It was originally used in B Language

• 1971 Since, for B Language To transform

  • In the newly bought PDP-11 On the use of B to B Write extensions , be called NewB
  • 1973 In, the main body will be basically completed , Change the name to c Language
  • They use the compiler and language at hand to PDP-11 Rewritten a Unix Kernel
  • Machine language and assembly language are not portable

• c Language The program can be used in Any architecture On the processor

  • As long as the processor of that architecture has the corresponding c Language compilers and Libraries
  • Then cross platform compilation can be realized
  • That's what we call cross compilation today
  • This is it. c Language The reason why it could develop at that time

• B Language Nor was it created out of thin air
• B What does language come from ？

Basic Combined Programming Language(BCPL)

• B Language comes from BCPL(Basic Combined Programming Language)

  • 1967 By the University of Cambridge Matin Richards Make
  • Also developed by Cambridge University CPL Language Improved from
  • BCPL It was first used as the of Oxford University OS6 operating system The above development tools

• Later, through the improvement and promotion of Bell Laboratories in the United States, it became UNIX Common development languages on

  • Earliest BCPL The language looks like this
  • This is the notation The earliest record ever recorded
  • There is a similar 、 what n Things that are
  • What did the line break look like at that time ？

BCPL The newline for

• This is the newline character at that time

  • !*n

summary

• \n It's line changing

  • He corresponds to ascii The code of the character is (10)_{10 Base number}
  • His English is LF, intend Line Feed

• So I can freely control where to change my line ！

  • Can you make the following frame title ？
  • Let's talk about it next time ！