Probably manuscripts, although nowadays, it might be mass storage system.
s.i.
MSC is basically the older version for switching system where both user part and the control part exist on single node. MSC is now split into MSS and MGW MSS does the contol plane function and helps in establishment of call. Once the call is establised MGW take care of its continuty.
It is referred to as the SI system (International System, in French).
It's easier to write something when it is abbreviated, especially when you need to write it many time.
Shorthand
MSS
That would be the nervous system, specifically the Central Nervous system, more commonly abbreviated to CNS.
# Mses. This form follows the pattern of the plural form for the courtesy title Miss, which is Misses. # Mss has also been suggested. However, as mss is also an abbreviation for manuscripts it is unlikely to be found in, or come into, common usage.
Pangpanga
The Super Nintendo Entertainment System is often abbreviated to SNES.
The Reserve Bank of India (RBI) uses the Cash Reserve Ratio (CRR) and Market Stabilization Scheme (MSS) to manage liquidity in the economy. By increasing the CRR, the RBI requires banks to hold a higher percentage of their deposits as reserves, thereby reducing the amount available for lending and investment. Similarly, through MSS, the RBI issues government securities to absorb excess liquidity from the banking system. Both tools effectively help control inflation and stabilize the financial system by tightening the money supply.