How to implement backspace in shell

man ascii  can   find out  
Oct   Dec   Hex   Char
───────────────────────────────────────────
010   8     08    BS  '\b' (backspace)
040   32    20    SPACE
177   127   7F    DEL

 These three characters are our focus 

• backspace Both sides involved

 Initiating side  
	 Press down   Physics Backspace  Key 
 Operation side  // xshell  Corresponding to the operation side 
	 Erase the last character 

//  The general process is   The operator heard   Initiate side action ( It involves a putchar)
//  Operation side   Erase the last character  ( It involves three putchar)

Actual operation

 Initiating side 
	putchar(0x7F);
 Operation side 
	putchar(0x08);
	putchar(0x20);
	putchar(0x08);