The Superintendent of Documents (SuDocs) system is a classification system devised by the federal government for arrangement of their published materials. Unlike other items in the library collections, the SuDocs system groups documents together by issuing agency rather than by subject.
Focus on the Three Things You Really Need to Know about SuDocs:
 It is not a decimal system. The number after the point is a whole number.
Decimal vs. SuDocs Order 
Decimal Order 
SuDocs Order 
D 1.1: 
D 1.1: 
D 1.12: 
D 1.3: 
D 1.122: 
D 1.12: 
D 1.3: 
D 1.33: 
D 1.33: 
D 1.122: 
 If the call number is the same to a certain point, then varies, the order is: Years, Letters, Numbers. Until the year 2000, the first number was dropped from years, so those years have 3 digits. Beginning with the year 2000, years will be 4 digits.
Years/Letters/Numbers Order 
Example 1 
Example 2 
A 1.35:993 
EP 1.23:998 
A 1.35:R 42 
EP 1.23:A 62 
A 1.35:R 42/995 
EP 1.23:9144 
A 1.35:R 42/2 
EP 1.23:600/998103 
A 1.35:321 
EP 1.23:600/R9823 

If the call number stem (the numbers before the colon) has numbers slashed onto the base number, the base number comes first, followed by the slashed numbers in order. The same rule applies to numbers dashed onto other numbers or letters.
Slashes/Dashes Order 
Example 1 
Example 2 
C 3.186: 
EP 1.23: 
C 3.186/2: 
EP 1.23/A: 
C 3.186/7: 
EP 1.23/A2: 
C 3.186/73: 
EP 1.23/2: 
C 3.186/9: 
EP 1.23/22: 