Difference b/w DATA TYPE and DATA OBJECT & differences b/w TYPE and LIKE

Question

hai
can any one say the differences between Data type and Data Object.
And also differences between TYPE and LIKE
thanks
Gani

Answer 1

hi,
_Data Types and Data Objects_
      Programs work with local program data – that is, with byte sequences in the working memory. Byte sequences that belong together are called fields and are characterized by a length, an identity (name), and – as a further attribute – by a data type. All programming languages have a concept that describes how the contents of a field are interpreted according to the data type.
      In the ABAP type concept, fields are called data objects. Each data object is thus an instance of an abstract data type. There are separate name spaces for data objects and data types. This means that a name can be the name of a data object as well as the name of a data type simultaneously.
Data Types
   As well as occurring as attributes of a data object, data types can also be defined independently. You can then use them later on in conjunction with a data object. The definition of a user-defined data type is based on a set of predefined elementary data types. You can define data types either locally in the declaration part of a program using the TYPESstatement) or globally in the ABAP Dictionary. You can use your own data types to declare data objects or to check the types of parameters in generic operations.
     All programming languages distinguish between various types of data with various uses, such as ….. type data for storing or displaying values and numerical data for calculations. The attributes in question are described using data types. You can define, for example, how data is stored in the repository, and how the ABAP statements work with the data.
Data types can be divided into elementary, reference, and complex types.
a. Elementary Types
These are data types of fixed or variable length that are not made up of other types.
The difference between variable length data types and fixed length data types is that the length and the memory space required by data objects of variable length data types can change dynamically during runtime, and that these data types cannot be defined irreversibly while the data object is being declared.
Predefined and User-Defined Elementary Data Types
You can also define your own elementary data types in ABAP using the TYPES statement. You base these on the predefined data types. This determines all of the technical attributes of the new data type. For example, you could define a data type P_2 with two decimal places, based on the predefined data type P. You could then use this new type in your data declarations.
b.  Reference Types
Reference types are deep data types that describe reference variables, that is, data objects that contain references. A reference variable can be defined as a component of a complex data object such as a structure or internal table as well as a single field.
c. Complex Data Types
Complex data types are made up of other data types. A distinction is made here between structured types and table types.
Data Objects
      Data objects are the physical units with which ABAP statements work at runtime. The contents of a data object occupy memory space in the program. ABAP statements access these contents by addressing the name of the data object and interpret them according to the data type.. For example, statements can write the contents of data objects in lists or in the database, they can pass them to and receive them from routines, they can change them by assigning new values, and they can compare them in logical expressions.
       Each ABAP data object has a set of technical attributes, which are fully defined at all times when an ABAP program is running (field length, number of decimal places, and data type). You declare data objects either statically in the declaration part of an ABAP program (the most important statement for this is DATA), or dynamically at runtime (for example, when you call procedures). As well as fields in the memory area of the program, the program also treats literals like data objects.
        A data object is a part of the repository whose content can be addressed and interpreted by the program. All data objects must be declared in the ABAP program and are not persistent, meaning that they only exist while the program is being executed. Before you can process persistent data (such as data from a database table or from a sequential file), you must read it into data objects first. Conversely, if you want to retain the contents of a data object beyond the end of the program, you must save it in a persistent form.
Declaring Data Objects
      Apart from the interface parameters of procedures, you declare all of the data objects in an ABAP program or procedure in its declaration part. These declarative statements establish the data type of the object, along with any missing technical attributes. This takes place before the program is actually executed. The technical attributes can then be queried while the program is running.
     The interface parameters of procedures are generated as local data objects, but only when the procedure is actually called. You can define the technical attributes of the interface parameters in the procedure itself. If you do not, they adopt the attributes of the parameters from which they receive their values.
ABAP contains the following kinds of data objects:
a.  Literals
Literals are not created by declarative statements. Instead, they exist in the program source code. Like all data objects, they have fixed technical attributes (field length, number of decimal places, data type), but no name. They are therefore referred to as unnamed data objects.
b.  Named Data Objects
Data objects that have a name that you can use to address the ABAP program are known as named objects. These can be objects of various types, including text symbols, variables and constants.
Text symbols are pointers to texts in the text pool of the ABAP program. When the program starts, the corresponding data objects are generated from the texts stored in the text pool. They can be addressed using the name of the text symbol.
Variables are data objects whose contents can be changed using ABAP statements. You declare variables using the DATA, CLASS-DATA, STATICS, PARAMETERS, SELECT-OPTIONS, and RANGESstatements.
Constants are data objects whose contents cannot be changed. You declare constants using the CONSTANTSstatement.
c.  Anonymous Data  Objects
Data objects that cannot be addressed using a name are known as anonymous data objects. They are created using the CREATE DATAstatement and can be addressed using reference variables.
d.  System-Defined Data Objects
System-defined data objects do not have to be declared explicitly - they are always available at runtime.
e.  Interface Work Areas
Interface work areas are special variables that serve as interfaces between programs, screens, and logical databases. You declare interface work areas using the TABLES and NODESstatements.
What is the difference between Type and Like?
Answer1:
TYPE, you assign datatype directly to the data object while declaring.
LIKE,you assign the datatype of another object to the declaring data object. The datatype is referenced indirectly.
Answer2:
Type is a keyword used to refer to a data type whereas Like is a keyword used to copy the existing properties of already existing data object.
Answer3:
type refers the existing data type
like refers the existing data object
reward if useful
thanks and regards
suma sailaja pvn