VARIABLES

Global variables

• msg Every transaction is a signed message. In this object comes the data of said message (sender, value, etc.)
• tx values related to the current transaction
• block values related to the current block

Local variables

• They are those that occur during execution. In the EVM it is the part corresponding to volatile memory

State variables

• They are variables that are stored in the ROM portion of the EVM. It's persistent memory

DATA TYPES

Integers

• uint nonnegative (8 - 256 bits)
• int 8 - (256 bits)

Boolean

• true
• false

Address

• address This type of data represents addresses of ETH (20 bytes)
• contains methods like .transfer or .balance

String

• string

Bytes

• bytes