What's the significance of the "@"-sign in SAS?

[Syntas_error]

While taking a SAS practice exam I came across the following line:

input @1 Var1 $ @8 Var2 $ ''

What does the @ sign mean in this case? This wasn't in the literature.....

[novinosrin · Accepted solution]

In your case, it means

Read at(@) column 1 the value of var1 upto a default length of 8 bytes of character

Read at(@) column 8 the value of var2 upto a default length of 8 bytes of character

[Syntas_error]

And how would SAS interpret this if there were only say four columns?

[Reeza]

It depends on other settings as well, specifically the delimiter and informats.

[novinosrin]

Compiler creates a descriptor portion(metadata) with var names and physical memory address to hold values) known as PDV to hold an observation. As input executes taking the default length, var1 gets the value upto whatever there is for the 4 bytes as each column is 1 byte of char. The value of var2 would be missing.

Howeever, there is a caveat, the automatic flowover behavior can cause SAS to read the next record and read value for var2, which will cause unexpected results. This is overridden with a truncover option in the infile statement. I would deem this slightly out of scope for this thread imho.

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@Syntas_error wrote:

And how would SAS interpret this if there were only say four columns?

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[Reeza]

@ has dual uses within the INPUT statement. It can either indicate the starting column, or if it's trailing, it indicates to hold the line until released.
There's a traailing @ and double trailing @@.

The INPUT statement documentation covers most of it : https://documentation.sas.com/?docsetId=lestmtsref&docsetTarget=n0oaql83drile0n141pdacojq97s.htm&doc...