Please clarify my queries
My 1st doubt is as you know solaris have default 8 slices out of 8 slices in which slice the OS is stored. Like in windows if you select C drive the Program files are stored in C drive like that in solaris in which slice the OS is stored.
My 2nd doubt is at the time of installation why we create /swap, /usr, /var directories in different slices and why we allocate space to these directories. It is must to create these directories i know swap is used for memory purpose. If we are not create these directories OS is installed or not.
Though the root file system goes to 1st slice which is s0 by default and its standard which is followed, however it�s not mandatory. You can install the OS in any of the slice excluding slice s2 as this slice represents the entire disk.
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Swap is needed as its virtual memory, rest you can keep in same slice, however its imported to note that in case you have log which keep growing faster the its always wise to keep it in separate slice not to chock your root file system. In case you have lot of installing going then its equally important to keep /usr in different slice.
All above are the standard practice, however not a compulsion. Being an admin by seeing the requirement and the build document you have to take decision as what best suites your environment
C: isn't really a drive but a file system located on a partition that can be any of the four primary ones. Similarily, / can be on any of the 8 slices except slice 2 by convention.
The OS can be installed on a single filesystem (/). Anything else like dedicated swap, usr and var are optional although a swap partition is recommended.