DBCC commands presents and syntax in MS SQL Server

DBCC HELP (‘?’)
It show list of all the DBCC commands present in SQL Server.

OUTPUT:
Checkalloc, checkcatalog, checkconstraints, checkdb, checkfilegroup, checkident, checktable, cleantable,  Concurrencyviolation, dbreindex, dropcleanbuffers, free,freeproccache, freesessioncache, freesystemcache,  Help, indexdefrag, inputbuffer, opentran, outputbuffer, pintable, proccache, show_statistics, showcontig, Shrinkdatabase, shrinkfile, sqlperf, traceoff, traceon, tracestatus, unpintable, updateusage, useroptions

Example:
DBCC HELP (‘checkdb’)
Returns syntax information for the specified DBCC statement.
OUTPUT:

dbcc checkdb
(
{ ‘database_name’ | database_id | 0 }
[ , NOINDEX
| { REPAIR_ALLOW_DATA_LOSS
| REPAIR_FAST
| REPAIR_REBUILD
} ]
)
[ WITH
{
[ ALL_ERRORMSGS ]
[ , [ NO_INFOMSGS ] ]
[ , [ TABLOCK ] ]
[ , [ ESTIMATEONLY ] ]
[ , [ PHYSICAL_ONLY ] ]
[ , [ DATA_PURITY ] ]
}
]

DBCC execution completed. If DBCC printed error messages, contact your system administrator.