If the data is continuosly in data SET SAS would read the first WORDS only from each line in the `datelines' block and it will ignore the rest of the line. if we use Trailing @@'it will read completly.and another TYPE of trailing is using single @ this is a line hold SPECIFIER.

• Trailing @ is used to hold the record in input buffer to execute another input statement on the same datelines.
• Trailing @@ is used to hold the record in input buffer to execute same input statement on same datelines intel eof record.
• The trailing @ or more technically, line hold specifiers are used to hold the pointer in the same record for multiple iterations. 
• The two tyoes of line hold specifiers are single trailing(@) and double trailing(@@).
• The single trailing hold the record until it encounters either another input statement or end of the data step.

They are used for the records such as 

001F38 H

002 F 40 G

To read these values to the data step

Data example:

input @10 type $ @;

if type='H' then

input @1 id 3. @4 GENDER $1. @5 age2.;

else if type='G' then

input @1 id3. @5 gender $1. @7 age 2.;

end;

cards;

001F38 H

002 F 40 G

;

run;

The double trailing holds the until the end of the record.

Data example2:

input id age @@;

cards;

001 23 002 43 003 65 004 32 005 54

;

run;

If the data is continuosly in data set SAS would read the first words only from each line in the `datelines' block and it will ignore the rest of the line. if we use Trailing @@'it will read completly.and another type of trailing is using single @ this is a line hold specifier.

They are used for the records such as 

001F38 H

002 F 40 G

To read these values to the data step

Data example:

input @10 type $ @;

if type='H' then

input @1 id 3. @4 gender $1. @5 age2.;

else if type='G' then

input @1 id3. @5 gender $1. @7 age 2.;

end;

cards;

001F38 H

002 F 40 G

;

run;

The double trailing holds the until the end of the record.

Data example2:

input id age @@;

cards;

001 23 002 43 003 65 004 32 005 54

;

run;