ABAP grammar small review

TYPES: define type
DATA: define variable
range: abap special interval, the structure is SIGN OPTION LOW HIGH
table: internal table, sap memory table, this is a more important variable
like type: Specify the type of the variable. If you define an internal table, you can specify table of. If you define a work area, then connect to line of, etc.
field-symbol: Define a pointer, generally used when looping, loop asign

The following is an example of defining an internal table:

*1. Define the internal table by typetypes: begin of ty_header,sign type char1,option type char2,