After months of testing and delays, Ethereum's Constantinople hard fork finally went live at scheduled block number 7,280,000. Constantinople was initially expected to bring out five EIPs (Ethereum Improvement Proposals) - EIP 145, EIP 1014, EIP 1052, EIP 1234 and EIP 1283. However, EIP 1283 which was supposed to help in reducing the amount of gas required to run/execute smart contracts was identified to have security vulnerabilities and therefore wasn't included in the upgrade.
EIP 145
Introduction of native bitwise shifting that improves information processing
EIP 1014
Improved scalability by leveraging state channels to communicate with off-chain transactions
EIP 1052
Optimized large-scale code execution for smart contracts by allowing only the compressed code containing essential contract data to be checked instead of the whole code
EIP 1234
Reduction of block rewards from 3 ETH to 2 ETH and delay the "Difficulty Bomb" for 12 months