A few things were missing, but mainly, You need to use the keyword contract here is the example using your code: 

    pragma solidity ^0.4.23;
    
    contract YourContractName {
        
        constructor(){
        }
    
        function processData(uint num) public pure returns (bool) {
    
            uint _number = num;
            if(num == _number) {
                return true;
            } else {
                return false;
            }
        }
    }

Notice that this will always return true. 

Hope it helps