Global special variables and functions

In Solidity, there are some global variables and functions such as block, msg, tx, and gasleft. These functions and variables are accessible globally in all functions and modifiers of your contract. Any information related to the current block, transaction, transaction sender, and transaction initiation parameters can be accessed using these variables and functions. 

Using block and transaction properties

Special variables such as block, msg, now, and tx are globally available in all of your contracts and libraries. Your transaction execution sometimes needs information related to the sender/initiator of the transaction. In some specific calculations related...